I called Trijicon's custom shop today, as I was curious about adding tritium to a set of sights.
Basically, you provide the front sight and for about $85.00 plus shipping they'll send you back the sight with tritium insert.
smallest size sight they reccomended for their "Better Insert" was 3/32.
For the rear, they offer tritium in "bars" - either vertical or horizontal. They are about another $50.00 installed.
For your H&H Royal DeLuxe...? No, Definitely Not. Necessary for low-light shooting of your double...? Probably not. Cool...? Yea, definitely pretty cool on your Heym, Chapuis, Merkel, etc...