There is a product for Lionel, it requires you add the charging module and provide track power to charge the battery. I believe the actual BCR is still the same. I've been meaning to whack one out to see what issues I run across, but I don't foresee any problems. Since I make my own BCR clones, I'd just combine the charging circuit with the BCR clone.
john did you ever look into these?
The 9vBRLT 9v Battery Replacement Capacitor: (item #598)
I have used a couple and they work just like the regular BCR and no charging circuit needed. Just run a wire to the roller pick-up.