if memory serves, i think peter bought a complete OTA (the VX range) direct from orion optics (with the 1/10PV upgrade), in which case this is the link you want:
http://www.orionoptics.co.uk/VX/vx6.html
(ps you'd probably want to upsize the secondary as well for use as an astrograph - best to check with Peter as to what size he went with)