Taps and dies for the screws are around £280 for two sets IIRC, as they have to be made, I made enquiries some time back to complete some bits for Roger....... Oh and a two start tap you really need a jig to get it started or follow advice in previous thread use lathe etc but use a centre in the tail stock and wind in till it touches the centre of the tap.

If you have the eyes of a S**t house rat and patience of a saint and have a imperial cutting box on a lathe then its possible to make your own taps and dies,