Long dremel bits, where to buy?

The problem with the long 1/8 shafts is that the will bend and throw balance off. I think you would be over working a Dremel trying to port a cylinder head. They sell 1/4 electric grinders which would be more appropriate for that kind of work and bits would be more widely available. I have to admit it is probably 1 of the most useful tools in cutting bolts off with the bigger discs.