Been awhile, but last time i saw a Sunbelt catalog, i considered the prices a lil'high and it never had the most latest safety krabs etc.
It is nice to have gear, but; it can be a slow mover; and anything small could get 'lost' so should be locked... The main thing would be to carry expendable items; that yielded fair cash flow for the space they occupy and have high visibility. Rope and krabs are a fair start. Small slings are an expendable, small item too; but might have to develop that market. i'd consider maillon links and prussick cords, metal safety snaps, rope thimbles, wedges, start a book shelf of knots for sale etc., throw bags, throwline become expendable items too. Maybe a peavey/ cant hook, couple of curved Corona hand saws(talk up and test water for Silkys), a curved leather scabbard.
Some of above are less expendable, but small; and could have a larger target area than just arborists. Many industries could use tough, strong arborist (and other) rope and hardware, so try to let word out to farmers, boyscouts, hobbyists of all sorts, boaters etc. you have different types of rope and hardware, L-earn some knots yourself. Get bright colored ropes and white to give choice and the contrasting, bright colors layed out, hung so they have to get your attention on their own. Everytime anyone comes thru even half related to the gear and doesn't find something, write it down!
One of Jerry Beraneck's topping a tree at 150' that is still 7' in diameter; with his foot in a cast; can be a fair, cheap, attention getting background. You'd be best to support area advancemeant in climbing; to sell more stuff (computer lynx to free materials showing latest lines, knots, techniques, hang line with different named knots in it etc.). Keep eye open for local arborist that would be lit on fire by these ideas, and good Natured and appreciative enough to give ideas and talk it up!
Rope is the biggest, most expendable, abused, should be able to get on the fly and not risk life, limb or property because lost, compromised etc. i totally commend, and appreciate locals trying to have it there in case someone needs it right now as an option of doing something even less intelligent...