I did a search last year to find a truck camper rental near Denver but failed to find one (I think there was a company in SFO). I was after a company renting a TC + truck.
So I don't expect you will be very lucky.
There would also be the issue of people reserving a camper and turning up with an unsuitable vehicle (wrong length load bed; insufficient over cab clearance; no tie-down points: C-rated tires; orders a Lance 1050, turns up to collect it in a 2001 F150 SVT Lightning, etc).
So it seems to me there is too small a market combined with too many pitfalls to make a viable rental business.
However, never say never, and you might get lucky.
Another option (depending upon how hands-on you are): Assuming you could rent one, it is probably going to cost at least $500 per week. Alternatively could you find an old camper for sale for the same / less money? You could try it out for the season and throw it away afterwards (or sell it). You'd then have a better idea of whether a TC was for you and what you really need in a TC so when you go to buy you can be confident you are making the right choice.
Steve.