Hi ...
You might want to try the Google CSE custom search engine located in the top right corner below the words "Advanced Search". For example, in your case, I typed in the words cheek piece no4 to see what would happen ..
I only had a quick look, so I'm not sure what the exact content is about, however, it turned up a lot of threads. You may want to try some other search terms of your own. I noticed the second link talks about "Cheek Piece Screws" and sizes etc ...
Cheek Piece Screws
Also, check the article titled Mechanical Blueprints and Specifications for the Enfield No.4 Mk1(T) Sniper Rifle (click here) in the Technical Articles for Milsurp Collectors and Re-loaders (click here).
Regards,
Doug