Non vacuum petcocks are readily available on the ‘net. Measure the center to center distance of the mounting screws and look accordingly. I just purchased some 48mm petcocks for a project and they were about $75 a pair. This is a common change on XS 650 Yamahas. I think They use 48 and 50 mm depending on the year. MikesXS has them but they are more money. The petcocks are a bit nicer though. You can also purchase or fabricate adapter plates to use 1/4 bsp or npt petcocks. …British style. I have gone both ways on builds. Pay attention to where the petcock comes out, as the adapter/petcock combo sometimes creates clearance problems. I have never has much luck modifying the vacuum petcocks.