How can I find someone's ebay ID and who they have bought from?

I don't know much about EBay. I am trying to find out where my competitor buys his equipment from on EBay.

I don't know his member I.D. Only know my competitors name and company name.

How could I figure out this?

Thanks for the advice.

well better don't waste time in doing that - there are many sellers on e bay - try the ones who have the best feedbacks - you may even find someone who can provide better equipment than your competitor

you can not find him with name you need his user