Might have stumbled onto something the other day. I was looking for some W body suspension parts. Ended up chatting for a while with Erik of HT Motorsports. In the duration of the convo, the Bonneville came up and he readily stated that he had made up some 92-99 coil overs at one point. They didn't sell.
Point being.. they have been made in the past and probably could be made again.
If you need more info or want to try and get a set. The website is http://www.westshorefabricators.com/
I spoke to Erik, not sure if there'* other folks in the operation. Seemed like a cool and receptive guy.