You could browse the parts websites for matching numbers for the 2 models, or call to the dealer and ask them to see if the part numbers match. Better yet, measure them and see if they are the same. They probably are, depending on the year.
I had 2 broken springs (not like coils, BTW, more like zigzag rods) in my '85 380SE. Don't bother trying to weld them, as they are spring steel and need to be annealed first (which destroys their temper as a spring, and you couldn't do this anyway without torching the whole thing).
What I did was crimp some split tubing around the broken ends with vise grips. Worked great. I also added some coils stuffed with stiff foam to the outside corner to compensate for sag. This too worked great.
To change the springs, you obviously have to remove and disassemble the entire seat bottom, a real PITA. I'll bet you could repair and improve the one you have easier, faster, and cheaper. All I did was remove the seat (20 minutes), flip it over on the bench, and work away among the springs and wires. It went back in the car about 1 1/2 hrs later. Just my 2cent's.

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1986 560SL
2002 Toyota Camry
1993 Lexus