Rich,
You will be hard pressed to find a used boat trailer for sure. Hopefully Byron from Prestige would pop in and give some advice. While you may only use that trailer a few times a year, I wouldn't let that determine if you buy new or not. Check the usual internet sites and do a search for trailers. Also, try your local dealer, you may get lucky.
Kerry
"I would rather be lost on the lake than found at home"