When checking a bulb on my Breva, I noticed that one rear lens was cracked at the screw hole and held by silicone. I checked the other side and it wasn't much better, so added some epoxy glue to both and siliconed them back on. They are serviceable though not too pretty.
I shopped around and couldn't believe some of the prices that were listed (>£20) and Gutsibits has them for about 10 pounds.
Much squinting at images of indicators & lenses later and..
Turn signal lens for Aprilia RS, Tuono 50, 125, Runner, Beverly, Carnaby - price
£3.31It's a pattern/aftermarket part though fits well and I bought a pair, so that any subtle differences won't be noticed.
Replaces OEM AP8127633
Might help someone else.