Eddles -
I use tirerack.com for all my tyre info. But you're SOL if they don't carry the tire you want. When I got my
Continentals ContiProContact tires, I had to tell the tire-shop dude that they existed in 51 PSI. He called the warehouse and they had them later that day.
EDIT: If you get them from a shop, try to get the better quality tire valves. Supposedly you can get valves that are designed for higher pressure.
CarloSW2