I couldn't find any hard steel wire in town, so I ordered replacement part from Borton Volvo in Minnesota (1-2 day delivery from Minnesota to Iowa). Cost was around $5 (plus $5 s/h). The one I removed looked as if it had been fabricated by someone, so I don't think I can use that one as a comparison, but the new one was a U-shaped wire with a loop at each end. I attached this to the lumbar support in the same manner as the other side (loops toward the center of the seat and placing the straight portions of the wire on opposite sides of the plastic tabs on the lumbar support (it looks to me like they are there for that purpose). I then placed the bottom of the U in the similar tabs of the adjuster. When I tighten the knob it does not put any stress on the plastic lumbar support, but I can feel the support when I sit in the seat. Does this sound correct? After 20 years of Volvo 240 ownership, this is the first one I've done by myself.
Marlin