Nailed it: go straight to the source and order one from NS if you need it.
Has something happened to yours?
Normal wear and tear. Looks a lot like yours did in your blog TVPP. Admittedly I'm new the tavor, but I did a simple test to see if in fact the bolt hold open was contacting the bolt and bolt carrier that anyone can do.
Here's what I did, using a Q-tip apply a small amount of toothpaste (or any visible paste type stuff) to the top of the bolt catch no more than 1 mm thick. Then load a mag and fire 4 out of 5 rounds and take a look at the paste. If the bolt catch comes into contact with anything at all you will see a disturbance in the paste. Of course once the 5th round is chambered and the mag is empty, the catch will make contact and the test will be void. But it's in the last chambering/firing/cycling I believe the damage is being caused.
You can do the test by hand cycling with dummy rounds too. You can also apply slight pressure to the bolt catch while cycling by hand just to see how obvious the disturbance in the paste is when actual contact is being made.
Some guys might think I crazy but the toothpaste trick has been used for years and I work with metal everyday and have a pretty good understanding in metallurgy.
I believe most of the damage is from 3 things
1. Upon firing the 5 (or last) round has the bolt is cycling to the rear, the mag is already pushing up on the bolt catch , causing the scratches on top
2. The bolt cycling fully to the rear and cycling slightly forawrd to "smash" into the back of the bolt catch
3. Loading a new mag and pressing the release causing more scratches on top.
Above all else I think this simple boils down to the metal being to soft in the bolt catch, as every other bolt catch I can think of operates in the same type of fashion.
If all else fails and I can't get a new catch I'll try tig welding mine and potentially hardening it or just run it without the bolt catch.
Edit - I was using the infamous gen 1 and 2 mags that do infact slightly raise the bolt catch as seen in TVPP video