Seat Spacers for Mounting Wider Seat???

Looking for some ideas here. I am going to mount a new seat in my Foster Legend. I am looking to install a seat from a Foster Shadow which is about an inch wider than the Legend seat.

It will mount from the same tabs, but since it is wider I will need to take up about a half inch on either side.

Any ideas on what might be a good spacer to use? I was thinking about washers.



Maybe …
pick up a cheap HDPE plastic cutting board (dollar store?) and cut a chunk for each side, then use washers to refine the fit?

That’s a good idea. thanks.