I took my tank in to Thunder Reef, they sent it to a shop in Portland for hydro. Took about a week. I don’t remember the name of the shop in PDX but it was up on Barberton.
There will be several dive shops in Portland or pungent sound that can accommodate your needs. Just make some calls. Big scuba shops there.
Fire King has a portland location there Seattle location does hydros for EVERY welding Distributor in the Seattle area and I'm told there Portland location is simalar
https://www.linkedin.com/company/fire-king-of-seattle-inc