Came across this thread looking for tires. I know this thread is 4 years old.
If anyone out there in google world ends up here, you can buy from the bigfoot manufacturer, Florida Sailcraft. At this time, they only had rim for $45 and assembly for $130. No tire only option, and the spread on that is $65.
Shop the Bigfoot 21” x 12” Tire and Rim Assembly for Jet Skis Trailers and fl sailcraft. Get the perfect fit for your watercraft today!
floridasailcraft.com
I ordered the ones in post 17 on ebay for $65 + tax, free shipping, which is right in line with the florida sailcraft pricing if they offered tire without the rim.
These are the specific ones that I ordered. This link may be dead by the time someone finds it, if so, search for "Nanco N800"
The Nanco N800 is a slick-surface flotation-style tire for ATVs/UTVs. There is no local pick-up available. Manufacturers often will change item details and as a result may not update their pictures.
www.ebay.com
I'll try to remember to follow up down the road to say if these Nanco N800 worked out or not.