[TPIN] Add Water Key?

[dvjones]

I have an L.A. Benge (3) without a water key on the third slide.  I've tried to avoid altering the instrument in any way.  However, I really need a way to drain the third slide.  At present I am removing the two little stop nuts and pulling out the slide, which is not practical in a performance setting.  Can anyone recommend a top quality shop where I might have a water key added?  I'm in rural southwest Virginia and will probably have to rely on shipping.  Thanks, DVJ