Jim Thompson wrote:
I can't seem to locate a DP3T switch, toggle or slide that has
ON-ON-ON

All I can find is ON-OFF-ON types :-(

Can someone point me to a source?

(Cheap at one-off :-)

Digikey has plenty to choose from. E.g., 0.1A/12V slide On-on-on
DP3T for ~$1.
Products - Switches - DP3T - Slide - DP3T - etc