The middle ground here probably still requires the initial purchase of stock from your side as if it isn't being drop shipped then someone needs to hold the stock, unless you work on a just in time system. However, once this has been achieved you can create your own fulfillment and storage network delivered by a 3rd party that would prevent you from being impacted by some retailers not offering drop shipping. A 3rd party relationship with a business who can store your stock as consignment stock and deliver it to your customers may cost you some margin but it will save you from the hassle of holding stock yourself etc. So my recommendation here is sort of like an Amazon FBA model, except you replace Amazon logistics with a more affordable and smaller logistics partner to keep costs down.

There are a few online B2B marketplaces in the US to consider and which one you go with will depend on your requirements. Amazon Business: This is a very legitimate option now as Amazon looks to expand its offering away from just a B2C model, with a greater focus on B2B. You can offer unique discounts for businesses and a host of other features to drive your B2B business. ThomasNet: This is more for a traditional supplier/purchaser business relationship but may be a worthwhile avenue if you sell high volume or recurring use items Alibaba and eWorldTrade: Both Chinese based business so I am unsure of any implications on trading here from the US however there are a huge number of US businesses looking to buy on here and so they are atill some of the largest B2B platforms.