One of our Argosy-owning customers was down in Las Vegas, New Mexico about a month ago. He was visiting a pawn shop called L&M Pawn, where he found two 40lb aluminum cylinders for sale. I have no idea if they're still available or what their condition is (though I'd assume they'd at least need recertification and possibly OPD valves).
I don't need or want them (since we're looking for 30lb aluminum cylinders). If you are interested and nearby, call 505-454-1991 or visit at 511 6th St., Las Vegas, NM.