I'd start by finding a similar product and seeing what you can dig up on how well it performs in each respective location (wholesale club vs hypermarkets vs drug store chains, etc).
You can likely do this easier if you know of a publicly traded company that has a similar product.
Also, this might sound strange but going to a grocery store in the morning you will find tons of brand reps and such. They always have their handheld devices, running calculations and such. I'm willing to bet if you went a few times and struck up a genuine conversation, they could give you some really useful knowledge.
Lastly, just a thought but with such a high re-order rate, you should look up the strategy Jay Abraham used when he took over a company similar to icy hot (can't seem to remember the exact product). Anyways, they figured the average lifetime value of each client and basically gave away as many of the products as they could at just really low rates to get prime placement in stores and such. They'd include some sort of reorder coupon in the packaging and really made the business on the back end.
Best of luck and let me know if I can help any further!