Not wild ones. Isopods are "bioaccumulators", meaning that they collect potential toxins, including heavy metals, in their bodies over time. However, they are very easy to breed and make a great smaller feeder. You can either catch some wild ones or buy some online.
He'll be fine. If your cham likes them, you should consider trying to breed them. It's very easy, they are prolific breeders, and they are a good source of calcium!