Eesh, the chances of that are probably slim, bro. I mean, I get the look that you're trying to accomplish on a shelf, and I totally understand your desire, but it's really hard to change something that's as set as these templates. The usual formulas is:
if game = handheld; then case = DS.
if game = console; then case = UGC.
It keeps collections more consistent that way. You're just looking for a different kind of consistency.

Being a fellow Game Gear fan, I sympathize with you, and would be more than happy to slap together a basic Game Gear UGC template. But, beyond that, I can't really provide you with any sort of art big enough to take up a whole UGC cover, and I only have covers that I made myself for all of the Sonic Game Gear games, because those are the only ones I own, pretty much. Even then, they're all DS case sized, and upscaling them to UGC would probably look awful.

You might be best off if I made a sort of template that just had the purple stripes covering it, (I'm assuming that's the game box style you're looking for.) with a centered frame in the middle that would have the cover of the game. (Picture our
TurboGraphx covers to get an idea of when I'm thinking.) That way, it would be easy for you to take the covers already created on this site, and do a real simple copy-pasta job onto the UGC template without worrying about distorting the images with upscaling.
What do ya say?