I used to sell tools. Most every major tool brand makes extra long drill bits. They just don't fly off the shelves so they aren't kept me in stock. I would start with Harbor freight then Grainger and Fastenal, Sears. They will have the reasonable prices try this
Unfortunately the pimo one is no use to me and sears don't have on the right size :S All I need is the longest 2.5 - 3mm drill bit for my 10" stem, but I understand that I'm probably not going to be able to one as long as i need but I don't mind burning out part of it