How to install software which aren't available on the cache?

Hello ( new to nixos ), sometimes I want to use random software for which binaries aren’t available on the cache. what is the best thing I can do? the software is so obscure no people will write a package definition for it. can I create an “environment” or something where I can use that software? there are a lot of proprietory software which I do want to use but can’t since they sometimes distribute dynamic binary. Thanks in advance!