Some time ago, when I had just joined the Club and was browsing (as you do) I saw a request for information about bulb/lens paint as nail varnish had flaked off.
I have recently found some glass paint on ebay - £2.30 for a 15ml bottle - the vermilion is the correct red for rear lights - I need red bulbs as I have clear rear light clusters, and two of the bulbs have faded almost to yellow!
The paint is Marabu GlasArt Vermilion, obtainable from Quickdraw Supplies Ltd, 21-23 Salisbury Road, Totton, Southampton, SO40 3HX. As I said above, they advertise on ebay.
It says on the bottle (tiny print) that it can be used on acrylic also - this would suit the 'clusters'.