3/8" schedule 80 - PVC pipe

[DonRotolo]

Call a local plumbing supply house, they probably stock it.
If the yellow pages don't yield one, call a plumber in town and ask for the name of a plumbing supply house.

[FrankJ]

Pipe size does not have any logical relationship to actual dimensions. 3/8 schd 80 is commonly available at Home Depot, Lowes, & hardware stores. Typically as nipples rather than long sections of pipe.

Schd 80 refers to wall thickness. Be careful to not get the more common Schd 40. 3/8 pipe is .675" OD, schd 80 has a .423" ID