For best charge times, the stock cable/charger usually gives the best results since it's rated at 2 amps.
This article seems good at first glance: How to get Full Power Charge (Mobile battery, car, ...) for HP Touchpad! - webOS Nation Forums
You can use this app by JC Sullins to read the charge rate: http://goo.im/devs/jcsullins/cmtouchpad/apps/TPChargeTest-v1.0.apk
Also, stock chargers should be still available on HP's store for only $5 and used touchstones can be found for as low as $25.
There are still reports of issues with CM7/CM9 installed and the battery gets low enough for it to shut down so the best bet is still to keep a charge on it.