Needless to say (I'm knocking on wood) I have NO experience @ this, altho' I'm a retired Engineer and in US, there are car windshield repair places they have some clear epoxy that they fill in chipped windshield & smooth it out w/just with a small cloth. U might want to go & talk to them or scientific instrument repair place too. If not take two pics w/slight movement, so u can cut & splice the original. Tho' might be troublesome in Street Photography. Just my 2c. Good Luck & do let us know how end up resolving the issue.