It is prob easier to dind dealers in big, especially major cities (if you are in the US, probably the same in other countries). It really helps to have a network of friends, I think that's how most people find their dealers.
Cities like Philadelphia are experiencing an epidemic of drug use and addiction bigger than they can handle (see youtube videos), so it is probably easier to obtain these things there. But it does not mean it is without risk, it is still very advisable to know some people who can recommend a reliable dealer.