yes a bunch of them are open to public others are not
gfs, marlinn, donEd are open to public
rest. dep and jetro are not
but yes all of them have their own sale paper. and yes the items are cheaper - a lot cheaper - as compared to other stores but you have to buy in bulk
other than marlinn, I have been to others
I try to go often to just get a feel for ordering supplies and to know what to expect.
also there are loads of catalog / warehouse type of places. you can look at yellow pages type websites or google for them. unfortunately google is not the best tool yet as there are not many that have websites.
one word of caution, there are a few stores that I have run across that display restaurant supplies and open to public but are a rip off in terms of quality of ingredients or utensils
conversely if you keep an eye out you would be able to find stores that are not too prominent but have some really good things (DonEd was found by me during my regular visits to a computer store near by).
one thing that I have found is that not many restaurant owners are willing to part with their contacts / stores. the stores also dont advertise as they are dealing with a specific market segment that almost always find them. this is a lot true in dealing with ethnic food groups or specialized equipment.
but that is why we have forums like these where people are more than happy to point you in the right direction and who take competition as self-improvement / control