Either I'm stupid, or I'm stupid, because I cannot find Xaine after talking to literally every npc and looking at everything
I was afraid this might happen! So, I did give a few more hints if you talk to Zlip some more. He tells the player what the bug is supposed to look like, but quickly shifts gears to say he COULD be transformed into a fish.
This fish in particular can be found in town, once you take a look at the town's fountain, you'll notice an odd-looking fish swimming inside of it's pool. Get yourself a net from Loika, also found in town, to capture the weird fountain fish and bring him over to Zlip!
This will complete Zlip's quest and completely alter his vore scene to include his mate as a spectator!