[Kevan]

Run a trued tyre on a truer as slow as it can turn, drop superglue on then spread with a piece of wire then sprinkle bicarb powder all over the glue, a quick blast with activator, leave a few mins then true again.  Rock hard and will last miles.

[Top Down]

Or .... open an existing Humbrol tinlet, dip brush, paint tyre treads, clean brush. 1hr later, tyres done, with nothing new to buy. Sorry, I'm a cheapskate 

[Fluff]

I like topdowns idea , although I think colour choice would be of some importance  

Steve