What else is out there? I love BGC, but I just don't know what sort of extra materials are out there!
Two video games, one for Turbografx and one for PC-88 (costs would include translation and software solution to emulate the original system).
BGC role-playing game from R.Talsorian Games
A boardgame from the same using extremely abbreviated rules (cf http://boardgamegeek.com/boardgame/22742/bubblegum-crisis
The comic by Adam Warren. Not sure if still commercially available or not. Your impressions of it may vary a lot.
Rob Kelk lists a bunch of manga and artbooks: http://robkelk.ottawa-anime.org/bgc/original.html
BGC OVA Manga: Go! Go! Sabers Eight parody stories starring the Knight Sabers.
BGC OVA Manga: MegaTokyo 2032: Side-stories of Bubblegum Crisis Several ADP and KS stories, some serious and some parody.
BGC OVA Manga: Soldier Blue Contained within Bubblegum Crash! B-Club Special, also exists as a CD drama and a novel already translated into English (a copy can be found on Joanne Hedge's
website, apparently reproduced with permission from R.Talsorian Games)
ADPF OVA Manga: Deadend City Prequel to BGC which has been used to link many of characters together.
The first two would cost both translation and licensing, the latter two already have english versions, so it's a matter of licensing.
Bubblegum Crisis B-Club Special
Bubblegum Crisis B-Club Film Comic '87
Bubblegum Crisis B-Club Visual Comic '89
Bubblegum Crisis 1 Completed File 5
Bubblegum Crisis 2 Completed File 6
Bubblegum Crash! B-Club Special
AD. Police Files B-Club Special