Rear bumper

[ATLparanormalOG]

Hi everybody newb here. My mother's 97 88 LS has been sitting garaged for several years. We got it out and got it started today after replacing some fuel line components. I want to fix it up and give it to my daughter. Really doesn't need much as it's only got 97k, but it's going to need a paint job (which obviously I don't need to ask about here). But what really concerns me is that this was a Yankee car, and therefore the rear bumper is almost completely rusted away underneath the bumper cover. What's weird is that the impact absorbers appear to have escaped rust free. The rear bumper appears to no longer be available anywhere except probably as salvage. So what other GMS will cross over with this? Would I be wrong assuming that a 97 LeSabre or Bonneville would do and if so are there other years that might work?