I strongly suggest against using something to fix your wrist so that you can serve withy our condition. Even if you did, other parts in your arm will compensate, and you will develop other problems.
There are so many ways to play tennis without serving. You can play baseline points. You can do drills where one is up at the net and you have to pass him. You rotate every 5 points. There is also the Djokovic game (youtube it).