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Do you mean the metal brake tubing with nut, or a bracket that holds it?
If it's a rusted through bracket, I'd just make something out of metal sheeting or strapping material, a loop around the metal end of the soft hose, but the bracket is built onto the end of the soft hose so you could just replace the soft hose to have a new bracket, and if it is the original hose then it is probably due for replacement anyway. Here's an example with a picture of the bracket on the hose:
If the brake line itself, can either make a new run out of bulk brake line, or buy something ready made in the closest size available as long as not too short. Too long you can work with. Ready made means a straight piece that you bend by hand, literally can be bent without tools, to a similar shape to the old line. It attaches at the other end to the soft hoses at the left rear wheel area, above it.
When I did that run across the axle on my '98, I used AGS Poly Armour Brake Line, part # PAX-351, which is 3/16" x 51". It was a few inches too long so I put extra bends in it to take up the slack.
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