Likely (and this may not be the answer you want to hear) you'll have to roll up your sleeves and build it. It's the hallmark of good BGz actually, building from the ground up. Finding some thick and dense air tones which create the right mood, a nice rumble, some HVAC tones and fluorescent buzzing, maybe OS alley drips if it's a wet scene, some OS tire skids and spotted car moves (including doors), maybe some OS walla here and there and spotted reverberant F/S bys.
I've actually recorded some rather empty garages and to be honest, they are incredibly boring sounding.
I can personally say that when posed with the exact situation you speak of, and show an example of, this is the approach I would take 100% of the time. You never will find 1 or 2 sounds which work as-is for a BG. It's all about breaking down what the scene calls for, not just literally but figuratively as well, and layering it together the right combination of elements to act as one cohesive environment.