I have some ideas but they generally center around placing ground/ceilings/walls on an existing map (either a generic interior or an outdoor map) to create a cozy space for a small bar.
One thing I want to toy with when the Foundry is on Holodeck is making maps with buildings that have interiors you can access without a loading screen. The trick is recorating the outside to look like a proper building.
Agreed with LV99, It is completely reasonable to use any interior. Then block an exit on any map... You can place bartender areas and tables chairs even dabo tables..... If you want a unique mission, "joboo" make it yourself..
I have an outside bar in the final mission of my story-arc... plenty of patrons and dancing girls and the combat arena is waiting for you as well as the Orion Queen
There is a bar that is use-able in the foundry and I added lots of decorations and a ferengi bartender... there's no reason why you can't put a bar anywhere in a foundry mission... on any ground map except social zones which already have them...