Parker 51 Aero Mk3 - no clip/clip ring

[mike_maple]

Hi folks,

Got back into fountain pens a year back, with a couple of Lamy pens (an Al-star and a Safari) that I have loved using since and found them to be very reliable, much more than the Parker pens I have had for years. That said (may have just offended half the forum, sorry!), I have had an old pen in a drawer for many years now, I think it was my Granddad's. I got it out the other day to see if I could clean it up and get it working, and found that it is a Parker 51. This meant nothing to me, but I have since found that it is a classic pen and held in some esteem.
Parker51.png
After taking it apart, breaking the breather tube in the process (solid with ink so not much use anyway), and cleaning it all up to some degree, I spent last night finding out which variant it was - it appears to be (correct me if I'm wrong), a Mark III with a rolled gold cap. The end of the barrel is pointed, the clutch ring is narrow and serves no purpose, and the end of the sac guard is metal not plastic, which I think marks it out as a Mk3. As you can see, the cap has sadly no clip or top to it, which means the finger clutch is loose and usually stays fixed to the pen when the cap comes off.
Parker 51 cap.png
Although the pen is not particularly valuable, what with the cap being somewhat scratched, and having the ubiquitous black hood and barrel, I'd like to somehow repair it for use myself - it seems to write nicely, and it seems breather tubes are easily available. What I can't find though is any type of clip/top for it, unless I buy a whole cap off Ebay, and even then I don't know whether I could take the cap apart for the pieces I need (I gather a gold filled clip and gold top would be needed to go with the rolled gold cap). Can anyone give me an idea whether this is possible should I decide to do this?

Otherwise I'd just be happy with something to screw into the top of the cap to keep the cap assembly together, though I'd assume the jeweled screws that you see for earlier versions would not be the required size, as I believe the Mk 3 is narrower at the top of the cap than other versions. Any ideas gratefully received