Possibly not a great help to you but have you had a look at any of the parts diagrams for Gamo, like the ones on Chambers website? Might be possible for you to identify your model (there seems to be a few Hunters, some with suffixes, & a few Sports too) if you can, then maybe a check to see if there are any part numbers which are common to both might help answer your question.
Gamos kind of slid under the radar for me but are creeping in...... Had one in 22, the magnum, that I thought about converting to .177 but project stalled. I like the trigger units for some reason although quite a few don't seem to favour them much. Cheers