Caught between a rick and a hard place. You'll find many brand wholesalers in particular or manufacturers themselves will not supply to an eBay business or similar because because of the environment. So they are essentially protecting the value of their product and therefore able to maintain a strong offline sales avenue.
It's really a case of just keep trying I would suggest. Maybe try to steer away from the branded gear that is protected and look at unbranded alternatives which won't have the same level of market protection.