Hi Shain,
Yeah, it looks like the type of set is a "FuG Spr d" as listed on the OnWar site...
http://www.onwar.com/tanks/germany/tfmarder2.htmA technique for narrowing down a google search is to have words which can't be on the page. To do this you put a minus sign in front of the word. You can also put quotes around a string to insure that exact string is used. I did a search on...
"Marder 2" radio -control -controlled
...and got some good hits. One is this page from RJProducts selling add ons...
http://www.rjproducts.com/Catalogs/K59_Production/K59_Production.htmlThey don't have a radio add on for a Marder 2, but they do have a super set for a Marder 3, which includes a radio. OnWar shows the 3 had the same radio set.
Anyway, RJProducts has photos showing some of the details of the big set, including this one of the radio...

Maybe that'll work for ya.
Take care.