Are there any kinds of crayfish that are inexpensive (under $20) for a small freshwater fishtank?

My brother really likes lobsters- and I was thinking it would be great if for Christmas I could get him a “lobster” or crayfish to keep in his bedroom. We used to have fish, but haven’t for a while, but the tank is still in the basement. It’s a smallish tank (10 gallons I think) and it has a heater and filter. I don’t want to spend much more than $20, but I have no idea how much little crayfish cost at fish stores or what kind of environment they require, or if this is even a feasible idea with my budget. I’d like to have some idea of what I’m talking about before I go to the fish store though.