I've made a few myself from shop vacs, old vacuum cleaners, furnace blowers, and even homemade 100% from scratch using a corded drill to spin the axle the fan was on. Here are some vids of my
shop vac blower build: https://m.youtube.com/watch?v=H44U-Iag1mI
FREE vacuum cleaner blower build:
I wired them both to be variable speed with an 8$ dimmer switch, both worked great! The one I currently use is from a furnace and it works best of all. Also free.