Trijicon does do it, but it may be only their own stuff. I contacted them last year just to find out for when mine do go downhill. Here is their reply:
"Good Afternoon ***** Thank you for your patronage of Trijicon products. Currently, we charge $54 to re-lamp the typical 3 dot sight Trijicon Night Sight set. Reflex is between $150 and $200 depending on model and ACOG is between $250 and $450 depending on model. Service for any of our sighting systems is pending inspection and please use the following link to get return authorization.
http://www.trijicon.com/rma.cfm SincerelyEric LockhartTrijicon Customer Service Rep1-800-338-0563 x148www.trijicon.com"
I can't remember the other places that do it, but there are a few. I was looking for lamps for a SUIT and finally found them... ended up not getting the SUIT and thus not the lamps.
US Nuclear, I think, makes most of the tritium used. Tritium is some nasty stuff, and so you don't want to mess with it yourself. Very poisonous. The lamps are sealed glass vials, usually with a manufactured gemstone insert for color. But finding the lamps are easy. Installing them is the problem.
You could try calling US Nuclear and talking to their distribution people. They sell everything from bomb grade fuel all the way down to little nuclear "souveniers" that have a speck of your choice of radioactive element that can be measured with a meter (intended for physics classes). Of course the bomb grade stuff is heavily regulated, the souveniers are exempt.
Sorry I couldn't help more, but it has been a year. If you look around you will find the lamps, though it may be difficult to find someone who can safely replace them. Depending on the sight, it may be cheaper to replace the whole thing. Trijicon charges half what a new iron sight would cost --imagine what it would cost to replace them by someone other than the manufacturer? The only one that looks feasible is the ACOG --$250+ to replace tritium.
