You need to make a dummy of this script, with a similar looking output, as below:

tv-find-grabbers.output.txt

root@74aef7d0e929:/# /usr/bin/tv_find_grabbers
/usr/bin/tv_grab_se_swedb|Sweden (tv.swedb.se)
/usr/bin/tv_grab_ar|Argentina
/usr/bin/tv_grab_na_tvmedia|North America (XMLTVListings.com by TVMedia)
/usr/bin/tv_grab_fi_sv|Finland (Swedish)
/usr/bin/tv_grab_ch_search|Switzerland (tv.search.ch)
/usr/bin/tv_grab_eu_epgdata|Parts of Europe (commercial) (www.epgdata.com)
/usr/bin/tv_grab_il|Israel (tv.walla.co.il)
/usr/bin/tv_grab_fr|France
/usr/bin/tv_grab_dk_dr|TV Oversigten fra Danmarks Radios (2012)
/usr/bin/tv_grab_uk_atlas|UK - Atlas (atlas.metabroadcast.com)
/usr/bin/tv_grab_it|Italy
/usr/bin/tv_grab_za|South Africa
/usr/bin/tv_grab_pt_meo|Portugal (MEO)
/usr/bin/tv_grab_is|Iceland
/usr/bin/tv_grab_fr_kazer|France (Kazer)
/usr/bin/tv_grab_uk_bleb|United Kingdom (bleb.org)
/usr/bin/tv_grab_na_dtv|North America using www.directv.com
/usr/bin/tv_grab_nl|Holland
/usr/bin/tv_grab_se_tvzon|Sweden (TVZon)
/usr/bin/tv_grab_combiner|Combine data from several other grabbers
/usr/bin/tv_grab_fi|Finland (foxtv.fi, mtv3.fi, telkku.com, telvis.fi, tv.hs.fi, yle.fi)
/usr/bin/tv_grab_na_dd|North America (Data Direct)
/usr/bin/tv_grab_pt|Portugal
/usr/bin/tv_grab_huro|Hungary/Romania
/usr/bin/tv_grab_no_gfeed|Norway (beta)
/usr/bin/tv_grab_uk_tvguide|UK - TV Guide (tvguide.co.uk)
/usr/bin/tv_grab_hr|Croatia
/usr/bin/tv_grab_es_laguiatv|Spain (laguiatv.com)
/usr/bin/tv_grab_uk_rt|United Kingdom/Republic of Ireland (Radio Times)
/usr/bin/tv_grab_tr|T�rkiye - Digiturk (www.digiturk.com.tr)
/usr/bin/tv_grab_eu_egon|German speaking area (Egon zappt)
/usr/bin/tv_grab_dtv_la|Latin America Direct TV listings
root@74aef7d0e929:/# 

e.g. /usr/bin/tv_find_grabbers =

#!/bin/sh

# set to the location of your 'tv_grab_de' script
my_grabber_script="/usr/bin/tv_grab_de"

echo ${my_grabber_script}|My Dummy Grabber

Now restart tvheadend again, and see if it appears.