KRINK, probably best known for their markers designed for tagging, have a new product which may hit the market soon: Fire extinguishers. Writers like Katsu have used fire extinguishers to write huge, and soon any writer or random kid with some money to spare will be able to do the same.
As HYB points out though, these are already pretty easy for anybody to make.
Also, if you’re a fan of KRINK and KR (the artist behind KRINK), he’s got a show at Don’t Come Gallery in Australia.