Bartek,
If you are seeking business relation, Remember your every interaction is client engagement. Which means you can get your clients anywhere and everywhere if you have the right spirit and approach.

I got my first freelance client through Some Un expected conversation in the train. So keep looking.

Most Important where ever you have seen your client or met, Get the contract signed before you commit. I realised the pain of not having a contract is your 200% possibility of loosing the money you earned.