Lego Education does a spare parts catalog - but not sure if you can buy from it as a private individual. I used to use something similar when I was a kid - I co

Lego Education does a spare parts catalog - but not sure if you can buy from it as a private individual. I used to use something similar when I was a kid - I couldn't afford (say) a complete new pneumatic set, so I just bought a pneumatics parts pack from a mail-order catalog and used those bits with my generic technic stuff. (Another great resource is the ideas magazines they used to print - not sure if they still do - with loads of pictures of creations, but with minimal or no instructions).