Scavenge tip:

Mains fans are used to draw air out of computer cabinets - I'm taking about those 5-7 ft high metal 'server' cabinets - they are usually wired as a seperate pluggable unit. Can be found at places that recycle such second hand cabinets. Duct tape will easily hold them in place for a few months, if you mount them on a board or piece of plexiglass.