Zoho CRM has a fairly effective inventory management module, however it doesn't come default to the core CRM offering and will tack on an extra charge. There's an info page on the module right here.
I am not sure of the specific functionality you would require in both the ERP or CRM, but I would suggest that you take a look at Blue Link Elite (www.bluelinkerp.com). Blue Link is a complete ERP solution for Distribution and has a pretty extensive CRM capability also.
A good example is BPMonline. It has a cohesive vertical for inventory management – bpmonline distribution.
The solution provides you with the tools and processes that you need to optimize purchasing and maintaining an inventory of goods, stock holding and reduce costs. The software has been designed to provide tight control of requests for all products that are below minimum stock levels.
Check it out at http://www.bpmonline.com/industries/distribution