You can find everything you need at the auto parts stores.That’s kind of what I figured. I tried looking at this stuff on some parts store websites and nothing fit. I’d love to just get one from Volvo if I can. Can’t seem to find it just looking though
You'll need a straight section of line, the appropriate metric flare nuts, a line cutter, and a flaring tool. A cheap $30 over the parts counter tool will work fine to get you out of this jam. You'll want to buy the appropriate fitting unions so that you don't have to replace the hard line all the way back (unless you do want to...).
You'll cut the stock lines at a good, easily accessible spot, install the union nuts, and flare the line. Then, install the union, cut your length of replacement line, install the nuts and bend it accordingly.
If your v50 uses the same flare as my 850, it will use a bubble flaring tool. If you show me a picture of your new steel hoses, I can confirm - take one with you to the parts store to make sure you get the right stuff.
Also, with the rust, pb blaster helps, but some heat will do wonders... And cycle the two for even better effect.