Mark,
Tritium sights are simply regular steel sights with a hole drilled and a lamp or capsule that contains the phosphorus and tritium (the tritium only makes the phosphorus glow continually) is secured in the hole typically inside of a rubber type gasket to help with shock absorption.
ETA: I just took a quick peek at the Amerigun sight and they are now installing Trijicon and their own sights as well as doing the custom tritium installs in customers guns. They have a price list posted and near the top of page 1 is an option for tritium bar with replacement rear sight for $117.50. Assuming a front sight of adequate width is obtained I see no reason they wouldn't install a tritium bar.
They were super polite and up front about what they could or couldn't do and I'm sure your not the first to ask for that arrangement.
Thanks for the info there! For the longest time I have wanted, and wondered about, a Tritium sight that was less coarse than te typical round dots. I am sure that for man sized targets at 7 yards large dots are wonderful. But to make a ribcage shot on a big game animal or remove the head of a small animal (not to mention informal plinking at spent shotgun shells, golf balls, parts of broken clay pigeons etc) they leave much to be desired.
I may have found some perfect sights for my near (still in need of action and trigger tuning) perfect revolver!
