Now here's an idea: go to the local welding supply and see if you can buy a couple older tanks, ones that have passed their renewal date. Compressed oxygen tanks are rated to hold a couple THOUSAND psi. They are tested regularly, but after a certain date expire and can't be used. You could plumb a couple of those together to use as air reservoirs. Even if they have a diminished capacity, they should still be good for a couple hundred PSI easily.
You need to drain your air tanks on a regular basis. If you do, you won't get water in your tools. The water filter helps, but they still need to be drained at least 2-3 times a year (depending on your climate -- here in Mississippi on the Gulf Coast I have to drain monthly).