For the 39, you can send your slide to Tool Tech who will drill the front sight and install a vial. The rears may be available out there, but I don't know. (I only use a tritium front on all my guns that have night sights)
As for the 19, if it has a red ramp, that can be driven out and I think Meprolight makes an insert with tritium for that as well. Again the rears seem to be available.
If you don't have a red ramp, you could send the 19 to Tool Tech for the same service. I hand-cut a dovetail in a 10-5 front sight base, which seems to have less material than the 19 does, so it would actually look better and be easier to mill off the 19's front sight and cut a dovetail in it's place, and install a tritium sight there.
I did my Beretta 92 front sight myself with a hand drill. Drilled out the front and installed a tritium vial in it. $15.
You can get your mitts on a 39-2 slide pretty easy on eBay or other sites and have a gunsmith either cut a tenon and install a 1911-style tritium sight or cut a very shallow dovetail and do the same.