Ok, they appear in the GBC game (as do some other Adventurers characters like Gabarro and Rudo Villano). And the GBA game... Well, we'll get to that. But what about PC/PS1?
I got some of the original LI2 PC Maya models a while back, and while I can't actually open them due to not having Maya (lol), I looked at them in notepad++ and there's mentions of "SBOOTS" and "SENOR" along where similar things for other characters are listed:
connectAttr "SBOOTS_LOD_cameraView3.msg" ":perspShape.b" -na;
connectAttr "SBOOTS_LOD_walk1f_cameraView3.msg" ":perspShape.b" -na;
connectAttr "SBOOTS_LOD_cameraView5.msg" ":perspShape.b" -na;
connectAttr "SBOOTS_LOD_conga2_cameraView3.msg" ":perspShape.b" -na;
connectAttr "SBOOTS_LOD_conga2_walk1f_cameraView3.msg" ":perspShape.b" -na;
connectAttr "SBOOTS_LOD_conga2_cameraView5.msg" ":perspShape.b" -na;
connectAttr "SENOR_LOD_cameraView3.msg" ":perspShape.b" -na;
connectAttr "SENOR_LOD_walk1f_cameraView3.msg" ":perspShape.b" -na;
connectAttr "SENOR_LOD_cameraView5.msg" ":perspShape.b" -na;
connectAttr "SENOR_LOD_conga2_cameraView3.msg" ":perspShape.b" -na;
connectAttr "SENOR_LOD_conga2_walk1f_cameraView3.msg" ":perspShape.b" -na;
connectAttr "SENOR_LOD_conga2_cameraView5.msg" ":perspShape.b" -na;
There's also this card in LI2 GBA which is rendered from a proper model of Slyboots as he would appear in the PC version (like the rest of the GBA cards):
I haven't ever collected all the cards in the GBA version - is there one for Senor Palomar too? To get this screenshot of Slyboots's card, I just used savestates to grind picking up the card near Pepper's house at the beginning of the game - which actually only took like three or four tries, actually. But I'd rather not keep doing that until I've seen *every* card (or at least Palomar's, if there even is one)...
Edit: lol screw it I'm grinding for cards via savestates anyway. I think this is the DJ...? The textures and hair are different though - he's got a classic sunglasses face, neato!
Edit 2: Unsurprisingly I'm only getting a small selection of cards. Ah well, I was hoping they'd made it truly random.