Rear wiper issue...Installing new motor

[95BlackTahoe]

I have a small problem. I have to replace the rear wiper motor on my Tahoe, and I can not seem to locate one simple part. I need the piece that goes onto the glass (almost looks like a filler plug) and a bolt goes through it. The motor I got from the yard didnt have it, and mine wont come off without snapping...

Anyone know a part number or something for this?

Thanks

Shawn