I think the best "off the shelf" stropping compound is the green sticks. Chromium oxide is what's in it and always a rich green color. I managed to find a stick of it at a local home depot/lowes one day.
My unscientific observation is that chromium oxide is the most often mentioned stropping compound in the forum so I assume it is the most popular. It has been available in stick, liquid and powder forms. I prefer the powder which I suspect is the most concentrated form, free of the additives necessary to makes sticks and liquids.