Two points for brandifer and thanks to the rest of you that encouraged me to check what was behind the pharmacist's counter.
I went to the grocery store and looked for those cards that you take to the pharmacist. I don't know why I didn't see them the previous time I was looking - I cite a cold-addled brain. They only had something like 8 different products in card format, so I selected Sudafed (it's a pun, see? pSeUDoEPHEDrine) and trotted up to the counter. When I got there, I noticed that they had Mucinex D on the pharmacist's shelf, but without a card.
The pharmacist had to do some math to determine if I could buy both Sudafed AND Mucinex at the same time, and was concerned that I was buying TWO cold remedies with the same ingredient. No, I'm not planning to take them both at once.
After taking the Mucinex, I had a good evening of no noticeable symptoms, and I just about slept through the night. I'm not doing quite so well this morning, but I'm happy to have the medicine cabinet replenished.