Vulcan rear crew seat parachute
 

Bit of a long shot but I am hoping that some of the ex military techs might be able to help on this. I am trying to locate a parachute pack and harness for a Vulcan rear crew seat that is displayed in our aviation museum. The seat is the later modified swivel type with the assisted egress system. We have been told that the parachute is an Irvin BK Mk 46/ 49 but can find no information available and even Irvin were unable to help. Can anyone confirm the correct type, part or stores ref numbers? Were they used on any other aircraft? Any information would be greatly appreciated in helping us locate the item.