On Amazon 30 by 40 precut stretcher strips are about $15usd, plus shipping.
You can find them similarly priced in art/craft/hobby stores here in the states. Or you can pickup some 1" x 2" strips of lumber and some 1/4 round from the hardware store and you could probably build one for about $3-4 each. Maybe less depending on where you live.
The same with the pliers, but it might be nice to hold the pair in your hand before you buy one if you plan on using them a lot. They cost anywhere from $15 for a cheap pair to $125+ for a more "pro" model. My advice is to not skimp here--you probably won't need the $100 model, but some easy to grip, ergonomic handles are really nice to have.