I'd like to have a couple more #20 propane tanks to carry me through the winter for power failures and camping. I can get a #15 pre charged at 7-11 for $49. That seems kinda high and it is only a #15. The other alternative is to buy a new one at Bi-Mart, Wal-Mart or elsewhere. Any one got a suggestion where I can get a couple new #20 tanks so I can take 'em down to a gas station and have them purged and filled? I've had bad experience with used ones, so new is the route I'd like to go...looking for the best buy or value. Suggestions?