I did fail, however, to track down a hanging scale, despite showing the picture around at several spots in the Jongno 3-ga and Jongno 5-ga areas. Store owners kept recommending different places for me to try and track the device down: a suitcase store, an electronics store up the street, etc. The best suggestion came during a weird, eerie, David Lynch-style exchange with one shopkeeper who spoke slowly and deliberately.
ME: I'm looking for this— (showing pic of hanging scale)
HIM: (pause) This is...
ME: A suitcase scale (gabang chejung-gi, lit. "baggage scale").
HIM: (pause) Ah. Right next door, there's a scale store. Nothing but scales.
ME: Oh, great!
HIM: (pause) But they're closed now. (This was at 4:45PM.)
Upshot: no hanging scale today, but I may go back either tomorrow—although the store might be closed on Sundays—or later this coming week.
Unrelated to the hiking trip, I also bought a clay pot to replace my horrible Daiso pot, as well as—finally—a stone mortar and pestle, which the seller proudly told me was made from native Korean stone. I also bought a second bamboo back-scratcher, which I'm likely to take on the hiking trip with me, mainly for its reversible shoehorn function, but also in case I need to scratch my back after wearing a backpack all day, and/or in case I need to smite any wasps or other pests that buzz too close while I'm seated somewhere.
Back to hiking. At this point, I've found almost everything I can hope to find in Korea. What remains are items I have no choice but to order from the States. An unnamed benefactor who works on base has kindly permitted me to mail items to Korea via his APO address, so I'll be taking him up on that offer soon—possibly as soon as the next two weeks.
This is good: I'll have my gear prepped more than a month in advance of the trip, which will give me a chance to test out my equipment and work out any kinks.