With the retirement of Kazuhiro Kiyohara, Karl "Tuffy" Rhodes is now the active leader in home runs in the NBP with a total of 442. Rhodes joined the Kintetsu Buffaloes in 1996 and moved to the Giants in 2004. He sat out the 2006 season (after going to spring training with the Cincinnati Reds), then returned to Japan in 2007 with the Orix Buffaloes. He is only the second foreign player to play long enough in Japan to no longer be considered a gaijin, at least for roster purposes (I think the first was Leron Lee, but I'm not sure).
I'm going to include a couple scans here, but Jason's really got this covered. Here's a couple of cards on his wantlist (which sadly I can't help him with):
2000 BBM 20th Century Best 9 #120:
2000 Konami Field Of 9 #FON00T-351:
2001 BBM Nippon Series #S55 (I believe that this is him hitting a home run in Game 2 of the Series):
2004 BBM Giants 70th Anniversary set (#092):