Hello 'jarczewski',
The best way I can think of is the Advanced search, - which only works if you know the
seller's user ID.
Up beside the Search bar's big Search button, click on the word Advanced.
Then,
Use the left column to search By seller or to Find stores if you remember the seller's
store name.
Have you ever bought from the seller before? If you have, the seller's user ID should be
somewhere in your feedback.
Good luck. 