Probably the reason you haven't found anything is because its metric. I have found some home depots and lowes with metric, but their hardware departments tend to get all jumbled, all those annoying little plastic bags... An Ace or similar home town hardware store where there's a dude behind a counter is best. Sears hardware has some too. Problem is the length... Might be hard to tell by eye, maybe get a couple different lengths? Hopefully some else with boards can give you a more precise answer on size.
