Recently there was long thread about the BCA. I can now post possible answers to some of the questions, such as "Why is the BCA still raising membership prices when there is a significant amount still left in its coffers?"
Beast are still going. Their Sidekick is a pretty useful tiny bag for carting your snacks and a bit of tat around long Welsh caves. It's 13l but I expect it's the one you're thinking of.
The MTDE mnipro I have is ~110mm deep x 210mm wide x 400mm high, measuring on the outside of the bag, which would come to about 9 litres external volume, not allowing for the scrunching up which would happen when fastening it up.