flush mounted switch
Look at the online Digikey catalog, page 2308. It shows the Apem line of vandal proof switches. I looked at several other manufacturers, and it appears that the required mounting hole is between .625" to .875", depending upon the switch. I think that mine was .75".
Don't let the prices shown shock you. Like I said, I went to a local electric supply shop, described what I was trying to accomplish, and he walked me to the back supply room with the boxes of inventory, reached in and said "like this". And it was exactly what I wanted.