An Auto Amazon Links extension WordPress plugin that allows you to ser a custom product URL.

auto-amazon-links-custom-product-url.php

<?php
/**
 * Plugin Name:  Auto Amazon Links - Custom Product URL
 * Description:  Sets a custom product URL. Edit the like of the plugin file saying "MODIFY THIS LINE".
 * Version:      0.0.1
 */

namespace AutoAmazonLinks\CustomProductURL;
class App {

    public function run() {
        add_action( 'plugins_loaded', [ $this, 'load' ] );
    }

    public function load () {
        if ( ! class_exists( '\AmazonAutoLinks_Registry' ) ) {
            return;
        }
        add_filter( 'aal_filter_product_link', [ $this, 'getCustomProductURL' ], 10, 1 );
        add_filter( 'aal_filter_unit_item_format_tag_replacements', [ $this, 'getProductElementReplacements' ], 10, 1 );
    }

    public function getTheCustomURL() {
        static $sCustomURL;
        $sCustomURL = $sCustomURL
            ? $sCustomURL
            : get_site_url( null, 'product1' ); // <-- MODIFY THIS LINE
        return $sCustomURL;
    }

    public function getCustomProductURL( $sURL /* , $sURLRaw, $sASIN, $aUnitOptions, $sLanguageCode, $sCurrency */ ) {
        return $this->getTheCustomURL();
    }

    public function getProductElementReplacements( $aReplacements /* , $aProduct, $oUnitOutput */ ) {
        $aReplacements[ '%rating%' ] = $this->___getLinkConverted( $aReplacements[ '%rating%' ] );
        return $aReplacements;
    }

        /**
         * @param   string  $sHTML
         * @return  string
         */
        private function ___getLinkConverted( $sHTML ) {
            return preg_replace_callback( $this->___getPattern(), [ $this, 'getLinkReplaced' ], $sHTML );
        }
            public function getLinkReplaced( $aMatches ) {
                return $aMatches[ 1 ] . $this->getTheCustomURL() . $aMatches[ 4 ];
            }
            /**
             * @return string A regex pattern.
             */
            private function ___getPattern() {
                $_sPatternHref  = "("; // first element open
                    $_sPatternHref .= "<"; // 1 start of the tag
                    $_sPatternHref .= "\s*"; // 2 zero or more whitespace
                    $_sPatternHref .= "a"; // 3 the a of the tag itself
                    $_sPatternHref .= "\s+"; // 4 one or more whitespace
                    $_sPatternHref .= "[^>]*"; // 5 zero or more of any character that is _not_ the end of the tag
                    $_sPatternHref .= "href"; // 6 the href bit of the tag
                    $_sPatternHref .= "\s*"; // 7 zero or more whitespace
                    $_sPatternHref .= "="; // 8 the = of the tag
                    $_sPatternHref .= "\s*"; // 9 zero or more whitespace
                    $_sPatternHref .= '["\']?'; // 10 none or one of " or ' opening quote
                $_sPatternHref .= ')'; // first element close
                $_sPatternHref .= "("; // second element open
                    $_sPatternHref .= 'https?:\/\/(www\.)?amazon\.[^"\' >]+';   // URL
                $_sPatternHref .= ")"; // second element close
                $_sPatternHref .= "("; // fourth element
                    $_sPatternHref .= '["\' >]'; // 14 closing characters of the bit we want to capture
                $_sPatternHref .= ')'; // fourth element close

                $_sNeedle  = "/"; // regex start delimiter
                $_sNeedle .= $_sPatternHref;
                $_sNeedle .= "/"; // regex end delimiter
                $_sNeedle .= "i"; // Pattern Modifier - makes regex case insensative
                $_sNeedle .= "s"; // Pattern Modifier - makes a dot metacharater in the pattern
                // match all characters, including newlines
                $_sNeedle .= "U"; // Pattern Modifier - makes the regex ungready
                return $_sNeedle;
            }

}

$_oApp = new App;
$_oApp->run();