For all you DIY folks who are looking for a momentary SPST switch that is totally compatible with standard wall plates, read on.
This is not a final solution, but it’s a step in the right direction.
Disassemble the cheapest Leviton on/off wall switch (about $0.69 at Home Depot. Do not get the “preferred” version (about $1.29 at Home Depot). The preferred version is glued together, as well as riveted, and cannot be disassembled without damage.
Remove the screw and fixture that has the long contact arm. Bend the arm up slightly and replace it in the body. The contacts will now be reversed with the contact buttons facing away from each other and the arm above the other contact rather than below it. The contact buttons facing away from each other is not a problem in a low voltage system. Remove the spring.
Make a plunger/chiclet to fit in the existing plastic body, with approximate dimensions shown below. The flare at the bottom is required to retain the plunger in the body and to prevent the plunger from wedging itself in the up position in the body opening. Note that my re-assembled switches have a curved shape to the face of the chiclet. I found this provides good feel and if it is oriented so the high point of the face is over the contacts, the chiclet pushes more easily as it slightly rotates on the spring bar.
Rivet the assembly back together. Viola! The feel isn’t perfect and if you use a piece of hardwood, the action is not super smooth, but it works. A chiclet made out of hard/smooth plastic should provide smooth action.
Anyone out there interested in making some 3D prints of the plunger and perfecting it?