Sig still sells Sigment.
Probably not for long, with their "ARFication"! Those buyers won't know how to fix anything or need glue.
FWIW, I used Sigment on a Starduster X wing, pre-glued all the joints, and it literally fell apart when I took it off the board. I went back over all the joints with Ambroid, and had no such problem. As for Duco, the late and great Bob White, F1B Ace, many time WC team member and World Champ was a Duco enthusiast. That's not to say that the current Duco is as good as it once was.

Steve