Not a lot of options when you're stuck with 27 inch. Those Pasela TG in 1 1/4 from rugerben's link look like a real winner for the price.

Those Forte's from Performance have mixed reviews both on their own site and from a thread here but mostly folks don't mind them and they DO reduce the flat occurances. So if you're on a budget then that may be worth a gamble.

But for a little over twice as much for the Pasela's I can personally vouch for how effective they are. I can't remember EVER having a flat with the Pasela TG's I've run and am running now.