What radioactive sources do you use and what do you store them in?

If you want to get hold of a strong Radium source in the UK a good place to look is on ebay - search 'Old WW2 aircraft instruments'. You need to be a little careful but I picked up a heavily radium-painted instrument for just £14, Look for a dark yellow/brown painted dial. Prices vary, some types being more popular to a collector than others - nothing to do with their radioactivity though so don't buy premium collectables.

*Treat these items with care, do not try to open the instrument to extract the radium-painted parts. The paint degrades over the years and there will almost certainly be loose paint dust inside which is a contamination hazard. The collectors of these things likely pay scant regard to their radioactive properties but you and I know better. Store it in a sealed plastic bag itself placed inside a labelled glass/plastic food container.

This is the aircraft instrument (?) I bought from Ebay for £14. It's a bit hot with ~1500cps (RC103) despite it being in a thick sealed case and also inside a plastic bag.