Targa Section Ring Help

[Inkyboots]

I recently acquired my first Targa, and after the initial thrill *whee* discovered that the ring that is supposed to sit between the feed assembly and the detachable collar is missing. While I am fairly certain this is an aesthetic feature, the gap is mildly distressing, and I worry that it may be important in securing the cap snugly, as in its present state the cap slides off a little more liberally than I'd like. (Pic attached in case I'm too confusing. I'm confused about the terminology.) So what I want to know is 1) Is this important, and 2a) Is there a way I can pick up a quick-fix thin metal ring-thing from a hardware store that will do the job of providing aesthetic continuity, and 2b) What dimensions would I be looking at?

 

 

 

Thanks in advance, guys and gals.

Ryan.E.M