It may not let you define what products are available per stockist. Not sure if you are selling directly as well or just providing stockist information as this would determine what kind of setup you can do. For example you could set inventory levels for every location but that would mean you are selling the products from those locations.
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If you don't have gazillion of collections, Storefolio could be a workaround. It is a photo-album style directory app, so you can display your stockist details in a grid layout.
On your requirement to search for stockist by products, Storefolio allows you to label each stockists, and let customers perform filtering on storefront. I'd imagine you can label each stockist with collection(s) associated with them, and the customers can then filter based on that. Below is a screenshot for your reference.