I have an older cast iron built-in tub the drain stopper rod and overflow tube is located outside the tub. The overflow tube comes through the floor and is covered by chrome pipe with a cap. A threaded drain rod comes through a hole in cap. The design is similar to a tower drain used with a claw foot tub.
The drain assembly has separated from the trap and needs to be replaced. I would like to replace it with another tower type drain/overflow. So far the only type I have found are designed to work with a freestanding tubs. If I converted it to a lift and turn stopper I will no longer have an overflow since there is no hole in tub also I would have 2" hole in my tile floor where the tower was. I am not sure if I am using the correct description when searching.
Any suggestion or help in locating a new drain would be greatly appreciated

Thank You