[construction] How could I run a 12 volt dc marine fan off of 120 volt ac power?

Is it similar to how a digital keyboard can be run off of batteries, but then uses one of those converters (cord with a little black box) to allow it to be plugged in to the wall. Could I make one or do they sell any DIY converters?

Also, is there a way to attach a sort of regulator of power (like a light dimmer) so that I can change the speed of the fan?

This is the pdf of the electrical specifications, it's the 1733 Series Turbo 3000:

http://www.attwoodmarine.com/userfiles/store/product/files/432/1731.pdf