From volume 94 of PSAS (1960/1) - an article about the cist slab found at Badden Farm, with its lovely carved lozenges. There's a photo at the end. The RCAHMS record says it's now in Glasgow Art Gallery and Museum. It doesn't seem to be on their website but I guess they've got a lot of items still to put on? It's rather unusual so you do hope it's safe don't you. Judging by the way the (pecked) grooves go through the pattern, that implies the pattern was inside the cist?
More illustrations at the bottom of the page here.