Bridgeport

I`ve bought an Interact.Don`t all laugh at once.Yes I know what I think of Bridgeports but I needed another machine for second opping and it was cheap and only 130 miles away in Newcastle so a quick trip down and back with the pickup,five minutes with the Fairy and it`s in position.It`s got a Heidenhain 150 original control complete with the normal "gross positioning error" message.I`m not bothered about the error message,it`s usually an easy fix.My problem is the Bristol Ericson (sp) quick change nut on the end of the spindle.All the screws except one and it`s sheared that locate the locking ring inside the nut are missing.Are they ordinary screws or have they got special ends?I`m assuming they`re quite tough.Are they available anywhere,does Bristol Ericsson still exist?Has anyone a spec/sketch of them? Mark