Does anyone know any good websites to find good used unis or do you recommend a new one i have one and am looking to upgrade…
The Trading Post in this forum will be the best resource for used unis I’d say.
Watch places you would normally find things popping up. Ebay will have things from time to time. Maybe Craigslist or the Classifieds in your area.
I think tho that as you get to the higher end unis that people who bought them are using them, or have destroyed them… 
Keld
a good unicycle website for cheap unicycles is www.unicycle.com