Getting into the industry as a small business

I own a small business mostly selling on Amazon. When I've tried to register to become a supplier with various sourcing companies hotels use (American Hotel Register, Avendra, Birchstreet) we get the cold shoulder. It seems like a catch-22 - we're not big enough to get registered, but we won't grow in the hospitality industry unless we get registered and start landing larger hospitality clients. We have a handful of clients, but would really like to grow more in this area and get away from Amazon in favor of a B2B model. How does one get into this industry with these roadblocks?