> ... where would be a good place to go for pre-punched valve leathers?

I can make valve facings most sizes for less than Player Piano Co.
did.  You would have to get and send me the leather to punch them from.
I can send you back what leather I don't use for your job.  Mike Madeira,
Leather Supply House, has a great selection of leathers to choose from.

I came up with a great tool for punching the center hole in valve facings
which many player piano rebuilders bought from me and are currently
using.  I also have a great 'set up' for punching the outside diameters
as well.  Sorry, I am no longer selling this tool.

Durrell Armstrong's death is a big blow to player rebuilding; we will
have to find ways to replace what has been lost to us.  My advice to
hobbyist rebuilders is to make up a business card which says you are
a piano technician (if you don't already have one) and open an account
at Schaff Piano Supply.

Bill Maguire