Polarstar finally made something available that is similar to what I want but sooo expensive

I may invest in a Polarstar later but for now are there any other cheaper brands of Co2/HPA semi-auto rifles I should look into?
Also are there any airsoft rifles here I could attempt to make?
I have a kobalt regulator and would like to fit the system into the body of an AEG so I could used its mags, barrel, and hop-up.
I care more about accuracy and range over looks and firing speed and have some experience with airsoft parts and simple air cannons.
Suggestions appreciated, Thanks