Hi Vitautas @CGngt ,
My suggestion would be to find some textures online, that you can use as alpha map, something like this:

(don’t use this one, I don’t know if it’s CC0 or what), You can also make them yourself if you want.
If you need to get really close, that might not be enough, but I don’t know of any other easy (or even not so easy) way of getting a decent result.
It really depends on the exact thing you want; in general, textures would probably be the best bet, but some special case might have another way that works.