The most common type found in the US is the underarm model. This type of crutch is usually used for people with temporary injuries. The forearm crutches are generally used for people who have permanent disabilities, at least in the US. Your doctor may also want you to get bariatric crutches.
One can also get platform crutches and knee support crutches. Crutches are usually made with wood, metal carbon and glass Fiber. They're great protection gear for medical relief, or support after sports injuries.
You can find used crutches on eBay. Make sure your doctor is ok with you purchasing a used set of crutches before you order. Once he does, look for the right set for you, whether it be a designer cane or just plain old crutches