Although I can't find it in the SBO chandlery, they marketed a conversion shaft with bushings that would adapt common sized rollers to the bow anchor roller. This adapter solves the problem of finding the correct width roller with the correct shaft hole in it. The right roller width is not difficult to find, but the shaft hole is usually wrong.
Before you buy an expensive custom roller, send an email to the SBO store and ask about the bow roller adapter. I know they have (or had) this product because I designed it. Attached is a picture of my adapter after several seasons of use.