I got mine from a local autoparts shop for £12, halfrauds sell it for around £16 but the can is half the size...
or Ebay
TAIL LIGHT TINTING (TINT) SPRAY BLACK BLUE OR RED NEW - eBay, Other Exterior Styling, Exterior Styling, Car Tuning Styling, Cars, Parts Vehicles (end time 17-Sep-07 12:33:17 BST)
Make sure if you use is, it drys in direct light such as the sun or leave the lights on in the garage etc, i didnt and when you dont the tint goes matt gray colour and not a shiny black, i had to sand mine down respray, laquer them and polish with a porter cableto get them looking like that.
If ilet them dry in the light t would be fine!
Learn by ya mistakes hey!