I sent one of mine into Sig to have it converted from DAK to DA/SA, in late 2020. They had the parts and did the conversion. So... seems like they could/would still work on one?
It's also worth noting that "The Sig Armorer" now offers a strut/seat setup for the P239.
https://www.sigtalk.com/threads/p239.../#post-5845538
So... in addition to smoothing-out the DA pull and making it a lot easier to swap out the mainspring (i.e., you don't have to F with the old-school, roll-pinned strut)... one of the hardest-to-find parts for the P239 (the P239 strut is unique to the P239, and not other Sigs) is now readily available.
I want to order some for my P239s. Just haven't gotten around to it.