Island petpets w/ the white/light base like the uni. It's too bad the Bika can't be made island (or @ least I didn't see it). I put up island caramiller, kimbi, and whinny.
For the xwee I think there's a pretty big pool of matches. But maybe you want to look at ones whose flames aren't only patterns on their body, just like here the xwee's ruff & mane are like real flames. Here are the fire weewoo, minitheus, and wibreth. I just realized the xwee has no red in its flames o_O hm.
I tried to find you some petpets from different price ranges and in different colors than the usual...fire and island...but i also have...fire and island petpets! lol....hope you like em':