A.C.
Ugh...the problem with LACK is that there are few options once you turn it on its side. I have one that I've turned into a bench but just happened to have some baskets that I had bought years before at Michael's that fit perfectly.
Some stores have a guide that matches baskets and bins to the shelving units, but I have had a hard time finding a good fit.
You could try the paper board boxes from KASSETT or NOSTALGISK lines. Or SAMLA plastic bins.