Ok, well, to be honest, a lot of these vehicles didn't carry unit insignia. Unlike the panzer Div's, many don't seem to have actually had unit insignia.
But, there was one unit in Italy that did have insignia, the schwere Panzerjäger-Abteilung 525.
This is one of there vehicles, this image is from the old Dragon kit
This is the decal sheet, I think the yellow shield badge is their insignia.
Of course, you don't have to put that, it may not have been on every vehicle, but it just gives you something to base yours on. This unit fought at Anzio.
Sorry, those links won't show, check the page here, you can see the decal sheet and the first of the two schemes.
http://www.perthmilitarymodelling.com/reviews/vehicles/dragon/dr6166.htm
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