A modern shelf support - produced from steel and nickel plated. Drill 5mm holes for the steel peg; so it doesn't go all the way into the work piece there is a flange in the middle and it supports the shelf on the same diameter 5mm peg. A good way of ensuring the shelf doesn't move is to rout a corresponding 6mm groove where it will sit on the support so it becomes captive on the support.
The overall length of the support is 14mm. Sold as pack's of 100 or 1,000.