How to find that one great coat; ebay keywords?

Trying hard to find one good full wool overcoat that would end slightly under the knee, yet I seem unable to find anything interesting. Rather slim (36 suit wise so would go with a 38) and 5'7, grey or navy, budget is student level.
The usual culprits in retail seem to mainly have slim shorter coats that lack any character so I turned to ebay, but I swipe through endless pages trying to find something cool.
For those who succeeded, what were your keys?

Thanks