I would consider a small compressor and just running a hose outside -- assuming you have electricty. Aside from that, we have always thought about using an outdoor vending machine (wrapped in a metal cage) for things like tubes, patch kits, tire levers, and maybe some cheap 15mm wrenches.
Things get trashed and stolen in our shops, I would hate to see what would happen to them outside.
--
Sincerely,
Jonathan Morrison
Executive Director
Salt Lake City Bicycle Collective
2312 S. West Temple
Salt Lake City, UT 84115
w: 801-328-2453
c: 801-688-0183
f: 801-466-3856
www.slcbikecollective.org