Frustrating A/C question (manifold gauge parts)

[alabbasi]

I have these old brass Robinair R12 gauge set that I use for charging my A/C. They work perfectly fine except that the lenses which are 3 inches in diameter and screw on to the gauges (3-4 threads) have become very cloudy to the point that you cannot see through them.

I'm trying to get replacement lenses which you would think would be simple enough as they are just basic plastic 3" diameter screw on caps. However, when I called Robinair, they said that they no longer manufacture them.

The only ones that they seem to have is the 1/4 turn type (PN# 11796) which I do not think will work with my gauges.

I'm quite sure that this should be a standard fitting so I'm wondering if anyone here has run into the same problem.

I'd hate to throw away a set of gauges just because the lenses are damaged.