Mope. Sleep.
If he can't figure out how to duplicate things he can divert a little bit of the water to run through a garden when water levels are unusually high and not otherwise, and figure out how unusually high they'll need to be to water the plants as often as they should be watered, and he can have a little garden, and he can supplement his diet of kittens. People who eat only rabbits die of a strange sort of starvation and it seems likely that this also applies to people who eat only kittens. Kittens and potatoes and greens? Well he can try it and see if it feels like he's starving.
Maybe there are wizards here who'll come and arrest him for doing magic errands for the locals. He doesn't remember what they do to you for that in Greece and it's not even clear it'd apply. He can't think how to check. Do some fireworks and see if anyone drops by to give him a lecture?
If he needs to wear these clothes to be acceptable in the city he shouldn't wear them outside of it; better to keep them in a box or something and change whenever he needs to visit. He'll go back, pick up his, figure out whether you can skin an okzo for when he needs replacements. The box, unlike the rest of these plans, is something he can start on now. He leaves his island to look for good sources of wood.