Steve:
As others have said, Lexel, which is available at ACE hardware stores, is one option.
Be advised that it does set up fairly fast....well at least to the stage where it forms "buggers"
If you need more working time, which often times you do, use our good old friend Proseal. Mask off with black electrician's tape where you don't what the stuff. I filled up a corner of a ziplock sandwich bag with the stuff and then cut the corner to the diameter that allowed the proper sized "fillet" of goop that I needed. Squeeze the bag and the stuff oozes out. Then I took a squeege and scraped off the excess and created the fillet between the glass and the skirt.
Either material is kind to plexi and equally important, will accept paint.
Regards,