Shop Aprons not only keep your staff, volunteers, and patrons clean, but they also keep people from accidentally putting tools in their pockets and walking out with them.
If someone spends a lot of time in the shop they might become particular about what kind of apron they use. There are some that have more pockets and some that evenly distribute their [and tool] weight using special back straps. For general use, get the simplest ones you can. Fancy straps only confuse new-comers, not to mention cost more.
Where to buy
Pedros and Park Tool make bike specific aprons, but thinking outside the box most tool manufacturers make their own too -- regardless if they make car or wood-working tools. You can even contact restaurant supply places to see if they have chef / cook / waiter aprons with a couple pockets.