This site for aviation enthusiasts has several great search engines. In the owner search database, enter the owners name as "last first" without a comma. In the multiple field registration search you can narrow your search by several parameters. Scroll down the index page and you'll find a certified pilots database. Not comprehensive, unfortunately, but not bad.
If you cn't find the airplane owner you're looking for in Landings, try the FAA's site. The registered aircraft database (where you find owners) is updated monthly from FAA sources. Search using the same rules as Landings