Mcmaster- carr probably has it, you will have to order online though. Super fast delivery...and they have everything you could think of. Check out their site. Yep they have it, order today and you should get it Monday.
Thanks for the offer to help, too, but I'd clean ya out - I'm stocking up from scratch to learn to do a variety of chores, one of which is filling pits on a pot metal trunk lid of all things. Also doing some "bubba" rescue work on the rifles.
(for my GTX - new ones are $1200-ish, so it's worth a little effort on my end!)
Unfortunately most of the HVAC supply houses wont sell to non contractors. You need to be a contractor or have a friend that is. What percent silver content are you looking for? Most brazing alloys come in different percentages most being 5% and 15%.