Alternate Dobsonian Altitude Bearings???

Typically when making a smaller DOB say 6-8", seems most builders will use PVC pipe sections. Then when building larger DOBS most builders see to use the very large semi-circlular wooden or aluminum framwork. Or just a large wooden circle with the formica attached. I wanted to know if anyone has found a readily available source for round "disks", or whatever they used for the altitude bearings.
Thanks
STeve

I used PVC for my 10" dob alt bearings and it works great. You can get pre-cut plywood discs at Menard's or Home Depot if you don't like to cut circles.