First off Joe you didn't say if it's one of the front or rear brake lines you have stripped and also what has stripped, the threads or the "nut" portion of the fitting.
I'm asumming it's the "nut" portion because you didn't use a flared fitting/line wrench and just used a regular opened end wrench, a line wrench is mandatory IMHO when working on brake lines or flared fittings so you don't strip the fitting, a line wrench is basically a boxed end 6 point wrench with a slot cut into it so you can slip it over the brake line and then slide it over the nut.
https://www.autozone.com/wrenches-p...4782!&ef_id=VtzcxAAABRAlJFJr:20171112051901:s
That all being asked and said, you can get new rubber and or steel brake lines at any auto part store, the steel lines come in straight pieces of various lengths, you just need to get the proper length and then you have to slowly and gently bend it to the correct shape to replace the damaged line, you need to take the old line with you so you can use it to determine how long the new brake line needs to be, also if you have never bent a steel brake line I would get 2 in case you mess up bending the line, if you kink the new line toss it in the trash and you need to start again hince the warning to bend it slowly, also steel brake lines comes with various fittings and thread types, you need to get a "Japanese" type of the proper size tubing and fitting size.
If it's the front steel line I can tell you, you will need a 8" replacement line.
Again that all being said be sure to buy yourself some lines wrenches while at the auto parts store, if you didn't strip the nut portion very badly it's possible you can still get a line wrench on it and get it loose and be able to tighten it again, you may need to use a small file to flatten the sides of the nut to get the wrench on it or you maybe able to simply and gently tap the wrench onto the fitting.