We've bought caves, and made caves, and found that different BN's prefer different types of caves, although the general consensus with them is that they prefer a tight fitting cave.
We've had spawnings in slate caves, plastic pipe caves, upturned terracotta plant pot caves, and cut in half terracotta plant pot caves. Even had a longfin that preferred to have the females spawn on the back of a box filter!! Didn't know we had fry till they started appearing lol
Basically if they are in a display tank, try and get the nicer looking caves, alternatively you can make your own and stick some of the substrate to it with aquarium grade sealant to make it blend in.