Primo Comets in 20x1.35 or 20x1.5 (100 psi)
Animal ASM in 20x1.9 (110 psi)
Kenda Kwest in 20x1.25 or 20x1.5 (100 psi)
Schwalbe Kojak or Marathon,
The list goes on and on. Try perusing this page:
http://www.hostelshoppe.com/cgi-bin/...ategory=701800
At 285 lbs, I'd gravitate more toward the 1.5" or wider tires, to reduce pinch flats.