On Topic theme - display header in sidebar layout on every page.

gistfile1.css

@media only screen and (min-width: 1024px) {
  .page #header, .single-post #header, .single-product #header {
    position: fixed;
    left: 0;
    top: 0;
    width: 25%;
    max-width: 500px;
    height: 100%;
    -webkit-transition: all ease-in-out 0.2s;
    -moz-transition: all ease-in-out 0.2s;
    -ms-transition: all ease-in-out 0.2s;
    -o-transition: all ease-in-out 0.2s;
    transition: all ease-in-out 0.2s;
    margin: 0 0 3.631em;
    padding: 3% 2.244em;
    clear: both;
    background: #2f2a2e;
    color: #fff;
    z-index: 999;
    -webkit-box-sizing: border-box;
    /* Safari/Chrome, other WebKit */
  
    -moz-box-sizing: border-box;
    /* Firefox, other Gecko */
  
    box-sizing: border-box;
    /* Opera/IE 8+ */
  }
  .page #header #logo, .single-post #header #logo, .single-product #header #logo {
    display: block;
    margin: 1.618em 0;
    max-width: 100%;
  }
  .page #header hgroup, .single-post #header hgroup, .single-product #header hgroup {
    float: left;
    margin: 0 0 1em;
  }
  .page #header .about, .single-post #header .about, .single-product #header .about {
    display: block;
  } 
  .page #header .about p, .single-post #header .about p, .single-product #header .about p {
    font-size: 1em;
  }
  .page #header #connect, .single-post #header #connect, .single-product #header #connect {
    margin-bottom: 2.244em!important;
    clear: both;
    float: none;
  }
  .page #content, .single-post #content, .single-product #content,
  .page .footer-inner, .single-post .footer-inner, .single-product .footer-inner {
    margin: 3em 10% 0 30%;
    width: 70%;
    max-width: 900px;
    -webkit-box-sizing: border-box;
    /* Safari/Chrome, other WebKit */
  
    -moz-box-sizing: border-box;
    /* Firefox, other Gecko */
  
    box-sizing: border-box;
    /* Opera/IE 8+ */
  
  }
  .page .layout-left-content #header, .single-post .layout-left-content #header, .single-product .layout-left-content #header {
    left: auto;
    right: 0;
  }
  .page .layout-left-content #content, .single-post .layout-left-content #content, .single-product .layout-left-content #content
  .page .layout-left-content .footer-inner, .single-post .layout-left-content .footer-inner, .single-product .layout-left-content .footer-inner {
    margin: 3em 0 0 2%;
  }
  .page #header #navigation, .single-post #header #navigation, .single-product #header #navigation {
    float: none;
    clear: both;
  }
  .page #header #navigation .nav, .single-post #header #navigation .nav, .single-product #header #navigation .nav {
    float: none;
  }
  .page #navigation ul.nav li, .single-post #navigation ul.nav li, .single-product #navigation ul.nav li {
    position: static;
    float: none;
    margin: 0 1em 0 0;
    zoom: 1;
  }
  .page #navigation ul.nav li a, .single-post #navigation ul.nav li a, .single-product #navigation ul.nav li a {
    margin: 0 0 1em;
    padding: .382em 1.387em!important;
    font-size: .875em !important;
    text-transform: none;
  }
  .page #navigation ul.nav ul, .single-post #navigation ul.nav ul, .single-product #navigation ul.nav ul {
    width: 100%;
    position: static;
    top: 100%;
    left: 0;
    z-index: 9999;
    margin: 0 0 1em 1em !important;
    text-align: left;
    background: none;
    box-shadow: none;
    -webkit-box-shadow: none;
  }
  .page #navigation ul.nav ul li, .single-post #navigation ul.nav ul li, .single-product #navigation ul.nav ul li {
    margin: 0;
    border-bottom: none;
  }
  .page #navigation ul.nav ul li a, .single-post #navigation ul.nav ul li a, .single-product #navigation ul.nav ul li a {
    margin: 0 !important;
    padding: .53em 1.387em!important;
    color: #fff;
  }
  .page #navigation ul.nav ul li a:before, .single-post #navigation ul.nav ul li a:before, .single-product #navigation ul.nav ul li a:before {
    content: '';
    display: inline-block;
    position: relative;
    top: -2px;
    margin: 0 .5em 0 0;
    width: 0;
    height: 0;
    border: 3px solid rgba(255, 255, 255, 0.3);
    border-color: transparent transparent transparent rgba(255, 255, 255, 0.3);
  }
  .page #navigation .cart-contents:after, .single-post #navigation .cart-contents:after, .single-product #navigation .cart-contents:after {
    line-height: 1.8;
    float: right;
  }
  .page #navigation ul.nav ul:before, .single-post #navigation ul.nav ul:before, .single-product #navigation ul.nav ul:before {
    content: none;
  }
  .page #header.keep-open ul.nav ul, .single-post #header.keep-open ul.nav ul, .single-product #header.keep-open ul.nav ul {
    display: block;
    visibility: visible;
    height: auto;
  }
  .page #navigation ul.nav li a, .single-post #navigation ul.nav li a, .single-product #navigation ul.nav li a {
    font-size: .857em;
  }
  .page #navigation ul.nav ul li a, .single-post #navigation ul.nav ul li a, .single-product #navigation ul.nav ul li a {
    font-size: .8em!important;
  }
  .single-post #content {
    margin: 0 0 0 26% !important; width: 74%; max-width: none;
  }
}