I started a thread about 3 weeks ago asking for advice with optics. Thanks for everyone input. I end up with 2 NcStar red dot sights. Even they are cheap, compared to real counterparts, I dont want them to be broken.
Here is brief list of my experience. It may be useful for you.
I had a link to sight protector, which connects to rail in front of sight. Dont like it. Firstly it feels flimsy, easy to brake, secondary it looks totally not cool.
Cool looking metal flush hiders are too dark for indoors.
Well, lets make own protection!
I bough 1.85mm sheet of Optics acrylic glass and test it. 340Fps BB point blank range went through and shattered all around. Dont use it, it will not hold well. I did not try more thick sheet, obviously Optics is too easy to shatter.
My second sheet was a Lexan 2.2mm. 2 hits made only a small dent less then 1mm diameter, barely noticeable. It looks like a small raindrop. I think I can have five of dents before I would need to replace protector. And it was hit at blank range.
So now we have a material. Draw circle you can fit into scope.
First you need to make a square using a hand saw.
Then cut corners using a pliers: make a cuts from both sides, then brake it with pliers.
You can use metal cutters. I did not have one, now I do, I think it will be easier.
EDITED: Best way IS to use metal cutters. It is fastest and easiest way to make desired shape. 12$ cutters will make a 25 minutes knife job a 5 minutes cut-and-fit exercise.
After 12 corners gone (4+8) you have a pretty round piece, all you need to do is cut and trim excess material on the side. Use sharp knife.
SAFETY WARNING. You still need your fingers later, dont you? Do not cut in direction of the fingers, you will end up in emergency. Use same technique as for wood cutting. Continue trimming till you fit into desired space.
Finish the sides with file. Now it is time to remove protective film
All took me an hour. Now I would do it in 20 min. My mistake was, I draw too wide initial circle, and end up with trimming over 2mm of extra material on sides.
My scope comes with front dust protector. It is a soft plastic tube with inner ring, preventing tube go deeper on the scope. I fit new BB protector in the front of inner ring, placed assembly back to the scope and now have authentic looking scope.
You see inserted BB protector down left.