I notice that you are from NZ; so my comments may not fit too well for you. In business, we used gear rack from Standard Steel Specialties,
Pricing for 1/2" x 1/2" x 6 feet length was $23.20 each in quantities of (2) pcs. in Feb., 2006. That was 20 DP, 20 degree Pressure Angle, a stock item they say. We used 24 DP on our machines. As for pinions here in the USA, there are Boston Gear, Martin Gear and Sprocket and others. We had our pinions made for us, and had them nitride hardened as ours was a commercial application.
If you do pursue R & P, there are some suggestions I might have in order to make it a good application. I am at jccinc-at-owc-dot-net