Since the OP has found his solution, I guess I can hijack this thread?
What about these minivan tires if my total weight is within comfort zone on these?
Its Kumho Sense Grand Touring radial, steel belted, $265 for 4, shipping $63 total w/o mounting $328. The Goodyear Marathon ST has weight of 1820lbs max, this tire slightly less at 1610lbs. I have a local low-cost tire mounting place where they service a lot of tractors and such could mount them.
I got a spare at Northern Tool and the generic tire and rim "look" ok but have no experience. Kenda Load Star w/ powder coated rim
FREE SHIPPING — High Speed Radial Trailer Tire Assembly, Spoked, ST205/75R15 | 15in. High Speed Trailer Tires Wheels| Northern Tool + Equipment
Locally at NT they are about $130 and with some coupons they send me I could get a good chunk knocked off that. Might get 3 more and relegate my present tires to spares. hmmm...