Oh, that's not allowed? A bridge to the mainland. I'd go visit every now and then.
Well, assuming I have an unlimited supply of food and drink, I'd want something to keep me occupied. If I could have wifi and a promise not to tell anyone to come rescue me, I'd be pretty happy for a while.
But who's gonna watch me keep that promise? I'll take this ginormous pile of books I keep in my room k thx
An island could be anything. Could be a bare rock of a few dozen square meters large. Hence the first object I'd request would be a cornucopia spewing all the food that I need.
But the whole thing would be more interesting if subsistence was a precondition. In that case I'd probably request some fellow people to share my isolation with. If this does not qualify as 'one thing', I'd take a musical instrument. Playing an instrument would be great to pass the time, and I might get really good at it.
Say if I'm on basically a huge floating rock with no plant life whatsoever, I'd want a nice box full of food and water to last me about a month, sort of what HahiHa mentioned, the box and its contents counting as one whole item.
