The Cubs were trailblazers of sorts back at the beginning of the 21st century as they (along with Mets) became the first teams to play a regular season game outside of North America. They opened that season in Japan with a two game series against the Mets at the Tokyo Dome. Prior to these games, the only regular season game ever played outside of the U.S or Canada was in 1999 when the Rockies and Padres played in Mexico. Since the 2000 Opening Series in Japan, there have been two other season opening series played there - in 2004 when the Yankees played the Devil Rays and in 2008 when the Red Sox played the A's.
The Cubs, playing as the visiting team, won the first game of that series 5-3. Shane Andrews & Mark Grace homered in the game and Jon Lieber got the win with seven strong innings. Sammy Sosa chipped in with a double and Rick Aguilera pitched the 9th for the save. They lost the second game, while playing as the home team, 5-1 in 11 innings for a not so ordinary season opening series split. The second game was a pitcher's duel with only 11 total hits in 11 innings. The most important of those hits was by Benny Agbayani, whose grand slam in the 11th off Danny Young provided the winning margin.
There are a few different collectibles floating around related to this series in Japan. I've pictured the ones I've seen below. I personally like the game ticket that is almost completely in Japanese.
Common Program (I think this is the Official one produced by MLB)
Uncommon Program (I think this is more of a bootleg program)
Homer Hanky given away to fans at the games
Japanese Action Figure Two-Pack sold to commemorate the series
May 2000 Vine Line