LOOK for Nurse Call buttons OR remote X-Ray trigger push buttons -- used in hospitals and medical centers.
These are also found surplus at hospital / medical equipment sales.

Switchcraft is OEM supplier for many of these assemblies.
Here is a page from their catalog -- new they run $10 to $20 depending on finish, cord, etc.
http://www.switchcraft.com/products/capc-8.html

97GVXXX06 -- Looks like XLR connector body with push button at end.

w9gb