There re some websites on where to buy toys under the General area. Check some of the answers to the questions there.
The best thing is to buy them on-line and choose a variety of toys. Make sure that they are size appropriate and get toys with soft wood and hard wood, chewable plastic, leather, woven straw or grass, paper, cardboard, and foraging toys. A lot of the toys have several different thing in them so you can see which part of the toy he likes. Keep a couple in the cage all the time so that he has a different things to choose from. Lulu likes the pinata type toy, and she loves to chew and demolish wood. I've also just recently discovered that she loves the straws from Dunkin Donuts. She rips the paper off and then chews up the straw. You can also get a swing, and ladders. There are so many toys to choose from, but eventually you will get to know what he likes.
Since he plucks go for lots of the pinata, and toys with rope and straw.