I quickly found what I needed and started walking around the store, looking for anybody who might work there. There was a door to the employee/backroom area, partially open, but nobody visible in there either.
I called out "hello" a few times -- even went to the door and opened and closed it to set off the electronic "bing". Nobody showed up.
So eventually, I found a piece of paper and pen, and wrote the following:
International Travel Adapters
[product code numbers]
No price tag on shelf
Nobody in store to help
I left my note, along with $8 cash, sitting by the cash register and walked out of the store with my "purchase". As we were backing out of the parking space, a couple of employees magically showed up inside the store. I went back in and explained what happened - they rang up my purchase, which was $17 and change.
Brilliantly run operation, that Radio Shack.