Hello - I’m a newby - I too am interested replacing the Tritium insert in my 1P29. Scope.
To start off with: The US Government considers Tritium to be a valuable commodity - and has regulations in place against wasting it.
I however have found a good source - Taiwan 🇹🇼 ROC. I ordered a Tritium glow pip for my car keys - I’m thinking a half sized version or so - might be useful for or needs. Please email me if interested. I’ve enclosed a picture taken in a dim room - you can see how brightly the insert glows - in total darkness it’s very bright.
Best Regards - fiftycal aka John Ritenour