I think if you go to the Hillsboro Goodwill expecting to find a lot of sewing machines and attachments, you might be seriously disappointed. I think they probably send all of that stuff to the shopgoodwill warehouse and not offer it locally. I was in my local Goodwill once and there was another customer in the store who stuck his head through the open door in the back where merchandise was stashed. A worker yelled at him immediately that he wasn't allowed back there and the customer asked about a guitar that he could see and asked how much they wanted for it. The employee informed him that the pile of things where the guitar was located was headed to shopgoodwill where it could be sold online where they could get "a lot more money for it," claiming they could sell that particular guitar for $1400.00. Only rarely do sewing machines appear in that store for sale and the ones that do become available are almost always in cabinets...that being said, I have picked up several nice machines in cabinets inexpensively, but they don't remain in there long at all (which, yes, is partially my fault). The shopgoodwills are divided by regions--I know mine is part of the "Goodwill Redwood Empire" with the shopgoodwill location being in Santa Rosa. I think the Columbia Willamette SGW probably has a large region which probably includes Portland and Eugene (and a lot of that I-5) corridor. They have probably also trained their employees to sort out those attachments for sale in lots.
OTOH, I could be completely wrong and Hillsboro, OR may simply be the other end of the wormhole where every lost attachment appears.
YMMV.