This is a good idea. I think the best way to 'distribute' the information would be to get permission to post a copy of the flier in a conspicuous place. Then give them a stack of fliers to keep on or behind the counter. When someone sees the flier and asks, "is this for real" they got to take a copy home with them.
The advantage to gun shop owners will be increased sales. When I purchased my Sig P220, I added the following items to my shopping list:
My local store didn't have any of these items in stock, and said ordering would take 2-3 weeks. They also would cost about 20% more than having them shipped from an online catalog. If demand for these items were higher, the store could keep them in stock. They wouldn't have to worry too much about price, as most people won't go looking on the internet if they can buy at their local shop. Waiting time is what kills it.
- mag holder (x2)
- Blackwahk rail system accessory platform
- Blackhawk CQC holster
- spare mag (the gun only came with 2)
So, one selling point to the gun shop owner/management is that promoting open carry enhances a niche market that they can turn a profit on.