Dred,
I would go with the Rubber Tires then. Get some with tread on as Artificial-I has said. Those on the link posted above by garen look ok.
Bear in mind that they will give alot better grip while they are brand new. This will ware off somewhat.
If you don't want to get the grip compound sources then try to keep the tires clean. Washing them in normal dish soap and water.Rinse them off well. Let them dry natrually and they will give very reasonable grip. Putting the grip compounds will give slightly more grip.
It's up to you how far you want to go.
I hope you have fun.
Menace