: Are there any bead and cove bits on the market that cut a 3/16 inch radius
: instead of a 1/4 inch radius?

I believe you mean "diameter" rather than "radius". If you are routing beads and coves in 3/16" thick strips, the 1/4" bead and cove bits do this just fine. The setup has to be precise, but once done, the beads and coves are very good.

I have not been able to locate any off-the-shelf 3/16" diameter bits.

Glen in Baie-St-Paul.