https://www.stage1restoration.com/product/rocker-molding-mounting-retainers-with-mounting-screws/ https://www.stage1restoration.com/product/rocker-chrome-molding-straps/ Mike Garrison has them as well, https://mrbuick.com/reproductionparts.html (Scroll down to the bottom of the page)
I actually removed all the small dents from mine sanded them down a little bit and moved up in grades. After 3000 grit I got out the polishing wheel moved to a fine polish tripoli. It probably looks better than original now.
There's a metal mounting strap that bridges the rocker and the fender. IMO, the repros are sub par. Better off trying to find an original set. It's not like it's a rare part
