No such thing as a stupid question here. The ID at the top is approx 12" wide by 10" deep. It's just over 20" tall. It tapers in depth to approx 7" at the bottom. Not these measurements are closest I could measure as there are a few convolutions here and there. Regardless, it doesn't appear your caddy will fit.
I use the bin on my performer for smoking wood chunks, gloves and such. Never store charcoal in there anyway.