Sourcing 1m reverse audio pots takes me back...to 2009 when I last bought some. I ultimately got a couple from G&L directly. At the time they were advertising that all their pots were CTS...but it turns out that even G&L could not get CTS to supply them. The ones they sent me were a brand I'd never heard of, as was the original in my bass. Since I wanted a pot with a push-pull switch, I ultimately "made" one by destroying one of the [CME?] pots G&L sent me to get the wafer. I swapped the wafer with the one in a CTS pot with a switch, and to my surprise and relief it worked fine.
Not much has changed in the ensuing 12 years. I could find a couple couple alphas and a TT from Mauser (all 16mm). I could get them directly from G&L for 2-3x the cost of getting them from Mauser. Something new was that I could get a Bourns with a DPDT switch from Digikey if I was willing to wait at 24 weeks. The store in Thailand is definitely progress ;-)
The weirdest thing is that it is relatively easy to get a reverse audio 3M pot...which I guess is used in some fender amps. If my Franken-pot idea had not worked, I probably would have used one of those with a resister across the outer lugs to get it to approximate 1M.