I bought a 36V 20AH pack from seller dy-power, includes BMS. So far so good, it measure out fine, meets AH spec at a 0.5A rate (that's all the power resistors I have), and charges fine. It's your basic duct tape pack for <$30/AH.
Received it within 8-10 days, well packaged.
Very fast response to all questions.
Anyway, just an FYI in case anyone is shopping.