I used to get PB Classic in 5-gallon pails from my local NAPA.
Another CI4+ oil is Mobil Delvac MX, which is only available from Mobil distributors.
These are high SAPS, high ZDDP oils that are not for use in engines that have aftertreatment systems. They were originally formulated for the first generation EGR engines.
These people (Texas Refinery Corp) http://www.texasrefinery.com/
will do mail order.
Their ProSpec III has massive detergency, TBN>15, sulfated ash 1.72%; too much for a spark motor.