Our Spitfire had a similar issue with its door light switch. The OEM part and reproductions were NLA except for the occasional (and quite expensive) NOS part on eBay.
You brought up the brake pedal switch. That happens to be what I used in my workaround for the NLA door switch. I bought the generic brake pedal switch from BPNW (MUCH less expensive than bought anywhere else). I made a plastic plate roughly the same size as the flange of the OEM door switch. The plate was tapped 1/2-20 to take the brake pedal switch and had a countersunk through hole for the door jam mounting screw. To mount the switch I had to loosely mount the plate and thread the switch into it from the back, then tighten the flat head screw. It was a fair amount of work but it gave me a working inexpensive solution. I barely had room to get the switch in from the back. I don't know if a TR-6 has similar access.
Sorry... no pictures. I can't even take a picture to send you. We sold the Spitfire last week!
EDIT: I offer this footnote for those wanting to offer other suggestions. I could be wrong, but if the TR-6 is like our Spitfire, the door light switch has two terminals that close to turn the courtesy light on. This is NOT the same as most cars where the door light switch has a single terminal and when the door opens, the switch closes, completing a path to ground via its mounting screw. This switch is basically insulated from ground and has two NC terminals which are "open" when the door is closed.
EDIT2: According to the Advance Auto Wire schematic by Dan Masters, the TR-6 LH and RH door switches are even more different than I imagined. I am leaving my earlier text for those it might benefit but it looks like the TR-6 used a driver's door switch with two pairs of contacts. One set of contacts is for the tunnel courtesy light, the other (like what I described above) is for the ignition key lock lamp.
Link to Advance Auto Wire TR-6 Wiring Diagram