@Shikaze: Nice find but yeah gotta agree. That doesn't exactly look like stuff I'd put on a Tempesta or any battle armor to be honest.
@Zenislez: I was pondering scanning it in, but that brings up the issue of image quality, which would be a pain. Possible but certainly not my first option (parents have the scanner). Cannibalizing other kits or buying waterslides separately might work, though typically HGs have pretty crap decals; I'd have to go Master Grade to get some or look hard for 1/144th ones.
Thanks for the input guys, really appreciate it. If you find anything, keep me updated, will you?