Here's a suggestion. Since you are already running 700x28 tires on your bike, get some the same size to replace them. I would recommend Panaracer Pasela TG Kevlar tires, which are available in 700x28 and larger sizes as well, such as 700x32. The larger tires might give you a slightly kooshier ride, but that has a lot to do with tire pressure. That is, you can run larger tires at lower pressures. Anyway, the Paselas are very durable tires that are flat resistant, with a little bit of tread, and reasonably light. In the 28s, Paselas TGs weigh less than 300 grams, which is pretty light. Just make sure you get the ones with Kevlar beads; the wire bead versions will cost a little less but weigh much more. Paselas are pretty easy to find for $30 each, and for $25 or less if you shop around.