as mine is cracked i am interested also.

I got a piece of 4 mm perspex and cut out the shape of the lens , I then cut a 15mm wide strip which I heated and bent around the dash cluster to form a rim ( edge ) , trued up the edge so it was flat and used araldite ultra clear glue ( sparingly ) to glue together. The plastic I used can be filed and sanded ( 1500 wet and dry ) and polished to a good finish .If you knew where to look you can tell its a 2 piece job . The secret is to use enough glue to fill all the voids but not so much that it flows IN side the lens , where it is really hard to remove without it looking obvious . I was fortunate that my best attempt was a push fit onto the dash