Considering your requirements for a cost-effective CRM with a B2B E-Commerce option, I'd recommend exploring SuiteCRM. It's an open-source CRM solution that allows for customization and integration, and it might suit your needs. SuiteCRM has various modules that can be tailored to your specific requirements, including those related to B2B E-Commerce.

Moreover, it's worth checking out this insightful article: https://www.cleveroad.com/blog/crm-implementation-partner/. It provides valuable guidance on selecting the right CRM implementation partner, which can be crucial in ensuring the success of your CRM deployment.

I hope this helps, and best of luck with finding the right CRM solution for your small B2B-Retailer!