http://cgi.ebay.com/ebaymotors/HEAVY-DU ... ccessories
You probably only need a 6 " stroke-I bought the long one 1st thinking I was gonig to the door direct with it. mocked up it would have taken 20 seconds for the door to open!
Outside the door I have a 2 panel 110v plug with waterproof covers-under one of the covers is a a dpdt toggle switch. they also sell remotes you use to acctivate it. Careful how sturdy you built things -this thing has enuff power to bent things. Notice the low tech piece of metal I had to weld to the door frame to cut down on flex.