RB67 lens caps

The rear lens cap from my (now dead) 90mm C don't seem to fit my new 90mm KL lens. Are there compatibility problems between C and KL lens caps?

Does anyone have a spare rear cap I could buy off them that would fit? Mamiya want £9 for one!

There are even among one focal length and the other. There are "flatter" (won't fit 50 mm) and "rounded" clip-on caps, and all different lock-in type caps. I have at least three different types at home.

Cap differences

The current Mamiya's seem to be different from replacements in that they have ears and lock on by twisting the mounting ring. The are available through B&H for about $8US new, and $5US used. There are off-brand replacements that are push on and may have difficulty with the K/L line in that the rear element barrel is a few millimeters larger than the C or non-C Sekor's. This makes them impossible to push on as the cap has a smaller internal ring that surrounds the rear element barrel as well as the outside of the lens itself.

http://www.bhphotovideo.com/bnh/con...&ci=472&ac=&Submit.x=13&Submit.y=12&Submit=Go

Just realised that I hadn't taken the extra ring for the pro sd off which I don't need anyway since mine is pro s. The old lens cap fits no problem without it