If you decide to stick with a regular tee I've found the Tanner Tee to be the best. Our rec league uses them and they can handle a lot of abuse.
Tanner Baseball and Softball Batting Tee
Tanner Baseball and Softball Batting Tee
IMO, the absolute best hitting aid is a hitting coach. Second is a plain basic $20 tee to hit balls off of for practice.
I like it except for one very important reason. The PVC pipe is DANGEROUS! I don't know if you have ever seen PVC pipe shatter but it turns into splinters.
I would spend a little bit more and use galvanized pipe.
It did answer a question I had when considering trying to make one and that is the use of the gasket rubber. One material I'd still like to find is the rod that the rubber is attached to. That needs to be durable and somewhat flexible.
Anyone else have any suggestions to make one? The homemade one would be great without the PVC.