I used to us a low temp silver solder, bought, at of all places, Sears. Used it on guns mostly. Cooled hard and very strong. I had a big supply and might even have a little somewhere. But, if you search for low temp silver solder I suspect someone still sells it. Then you can just use plain ole propane torch.
BTW, I heard that MAPP is no longer made or sold and some other stuff is now on the market.
I know whatcha mean about expensive for that oxy and (formerly) MAPP.
"Folks is funny critters."
Think for yourselves and let others enjoy the privilege to do so, too. ~Voltaire