I got in touch with the good folks at R Talsorian Games, and it turns out that they have their original source materials and can produce the BGC RPG and the two supplements (Before and After and AD Police) in PDF form.

Bubblegum Crisis - MegaTokyo 2033 RPG - Free ebook download as PDF File (.pdf) or read book online for free. Bubblegum Crisis.

They would like $2400 for the rights to include it in the set; that's basically $1 per set.
However -- and I need to emphasize this -- since their license to BGC has long since expired, a new 'character goods' license will be required. This may be easy (because it was licensed previously), or it may be difficult to impossible. No matter what, a character goods MG (minimum guarantee) will be required, probably in the $2500 range.
If it turns out there is sufficient interest, I'll put it up for a vote, and then go inquire about the licensing issues.