Welcome to the forum Paul. There was a seller on US ebay selling 1/4, 3/8, and 1/2 collets for a while so that is one possible source. As another member above stated there is a B&D model that is the same. You could try ereplacement parts to see if they are still available there. I did a quick search and only found the 1/4" collet (Amazon) but mine came with both 1/2 and 1/4. It's a nice little router. I've had mine for years.
Someone I consider a master woodworker once told me that a master woodworker is not someone who never makes mistakes. He is someone who is able to cover them up so that no one can tell.