It sounds as if you have a thriving business. My name is Harvey Justamann. I've been in importing and supply chain management for 25+ years. Of course an Excel model can be built to become a tool in managing your inventory. I do not think you will find a model that fits your business in a pre-made template. In order to make the best tool for your business many questions must be asked and answered. I have built many financial forecasts in Excel. I would be happy to give you some advice at no charge.
Best of luck,