Try any of the following:
www.sdp-si.com,
www.wmberg.com,
www.smallparts.com, and
www.martinsprocket.com. You can also use Industrial search engines such as Thomas Registry,
www.thomasnet.com and
www.globalspec.com. I have used all these sources at one point in my career and each can be helpful depending on what pitch and pressure angles you are after. Good luck!