If you can't find anything that works for you on Winnipesaukee try Moose Landing Marina on Sebago. I just bought a 25 foot pontoon boat there and they have quite a few new and used pontoon boats in stock.
https://www.mooselandingmarina.com/ The Sales Manager, Will Monson, is very good and easy to work with.
I am picking up the trailer next week at Trailer Outlet in Tilton and going to get the boat. Trailer Outlet has been recommended on this site before. I have bought 4 trailers from them over the past 15 years and they are always the least expensive. I shopped around for prices first but found Trailer Outlet to be about $1,000 lower than any other price I got.