All this resources are external. Can I get the NetHash by myself? Interesting how this resource - coinwarz.com is getting such data
Smell like you want to do solo mining. So you want to know Nethash of some coin, but you don't want to get it from public info that can access by all peoples, right?
Maybe you need to build your own pool (at a server or your local machine). As you said above, you can saw Nethash in a pool, but the problems are you want to see Nethash from a coin that you pick, and may other pool haven't added that coin yet.
So, you can use my advice above, just add the coin that you want to check to your own pool. Just find mining pool software that has those features. My old experience, I use MPOS. (but that was very old experience)
Some block explorer also showed Nethash. (FYI)
#clue 