It's close but unfortunately it doesn't look like there will be enough space for the 4mm round vials in this particular watch. This watch manufacturer built rather thin watches (for the time) and so there is only about 2.5mm to 3mm of vertical space to work with.
The round high pressure, high intensity 20mm by 4mm tubes would be impressive (plus they are available in "ice blue"). There is a seller on eBay offering 22.5mm by 3mm tubes (search on "Gardner Tritium" or "Tritium Max"). That just might work.
The flat tubes would still be neat. The goal is to have a watch that's easily readable at night, not one that you can use as a flashlight (even thought that would be cool).
-abe.