You can buy mouldings like this from diy stores, like focus. as far as specific sizes go, I'm not sure what they do. However, it would be pretty straight forward to make it exactly to your dimensions using a router table, if you have access to one.
@Sam_Doman started
London Fixed Gear and Single-Speed is a community of fixed gear and single-speed cyclists.
You can buy mouldings like this from diy stores, like focus. as far as specific sizes go, I'm not sure what they do. However, it would be pretty straight forward to make it exactly to your dimensions using a router table, if you have access to one.