Niagara Cycle Works has them .... think Kenda @ $5.93 a piece.

http://www.niagaracycle.com/index.ph...er_id=&sort=3a

S&H is about $10, so find a few other things you will need now and in the future (tubes, more tires, cables, etc.) to add to your order to "spread out" the S&H cost.
It is easy to do, since these guys have the lowest prices around on the same stuff everybody else is selling. Look through their "Clearance" section, and do a "price ascending" sort if you are bargain hunting.