Need Valve for B&H Euphonium

[Mamaposaune]

I know this is a long shot, but thought the repair guys here may have some ideas.
I'm in need of a 2nd valve (the entire valve, with bottom and top caps and the finger button) for a 1982 (I think) Boosey & Hawkes Regent euphonium.
It belongs to the community music school where I teach, and I just recently discovered it in a storage room. Someone likely donated it years ago, it's obviously been sitting for awhile.
Anyway, otherwise it doesn't appear to be in bad shape, except for numerous dings/shallow dents and being filthy dirty. (I can deal with the grime).
I have narrowed down the problem to the valve itself; the other 2 valves will fit and work in the 2nd valve casing.
I don't see it being fixable. Someone (not me) tried to get the stuck valve out with a sharp object, punching a hole through the bottom of the valve which went into one of the ports.
I would love to get it fixed to keep in my studio for my euphonium students!

[SoVTTb]

It’s possible to patch inside the valve port tubing if the puncture is all that’s wrong with it.