I usually stock up on such things before traveling, but I'm very interested (just in case I miss something) if there's a place on property to pick up forgotten electronic items such as this. Thanks for asking the question.
Been scratching my head thinking of anywhere where this might be possible on property. In short, I don't think it's possible, physically.
Your best bet if you don't want to leave the bubble is to order same or one day shipping to your resort from Amazon.
Or ask your resort concierge if they can pick one up for you. I shudder to think how much they'd charge you for that service though.
There is also a CVS right off property on World Center Drive. Just after it changes from EPCOT Center Drive, all you drive through are woods on your right and a golf course on your left, and it's at the first intersection, right across from the Caribe Royale resort. It's so close, I think you're still effectively in the bubble.
This advice is probably too late, considering you posted this 7 days ago, but for future reference figured I'd post it.
Well, it turns out that the TV in Pop has a hard-to-spot tiny joystick-button in the back which can be used to select input.
The problem was the rooms now have a dumb remote that can't access any advanced features, so, couldn't "mirra-cast" (send from laptop to TV via WiFi/Bluetooth) because there was no way to select input. So, I thought I needed an HDMI cable to do the trick.