Some thirty five years ago I worked in the next building to the original patentees and manufacturers, Saunders-Roe Developments Ltd, of the 'Betalight' as it has become known and in a pot in my stud box I have a few dozen of the large torch cells left over from those days still glowing well enough to read by.

The best place nowadays to find the raw tubes cheaply is as fishing float bite markers which here are known as "Isotopes" for some reason.

They are easily converted for markers with a drop of epoxy glue and a 'Crystal' ball point pen tube.

The Tritium gas inside is radioactive (no radiation escapes the intact tube as the glass effectively shields the beta radiation) and could cause problems in quantity but the amount in the tube is so small that breakage and release may be ignored. The problem is with storage of a significant quantity and possible breakage.

In the UK we had a rather nice telephone called a Trimphone that had its dial illuminated by a long curved Betalight. The phone company (British Telecom) were successfully prosecuted by the Government for having a full skip of thousands of scrap phones all with their internal betalights, way over their radiation storage allowance.