You can get Mets tickets right up until game time from StubHub.com for every game at Shea Stadium as well as any Mets game at any stadium in the league. Use this link to get hard to find tickets including division rivalry matchups late in the season and Mets playoff tickets, too.

http://www.stubhub.com/new-york-mets-tickets/?ticket_finder=5545

You can also purchase NY Mets tickets directly from their official web site.