Sounds like it will never be cheap enough for you.
People want money for materials and labour.
Repro glass cylinders are cheap, around 300.00 real ones usually 400-800 except the rare ones like for the double pumps, they can run up to 1000.00 or more for 1 cylinder.
Your best bet, get a pump missing a cylinder and run hail screens.
To try to build one on the cheap, usually looks just that..cheap. A lot of time and effort expended to build something very few people want, and will you really be happy with it?
Cheap globes are 70.00 , that is very cheap compared to real ones!!
Here is what 500 would bring in the repro market.. about 1- 12 hrs labour but you must deduct parts, material, paint, hose nozzle etc from that leaving even less for labour!