For more information on buffing compound, see our beginner site Common Woodworking.
Buffing compound is not always readily accessible and I was scrounging around in Harbor Freight (a national US chain of tool and equipment suppliers in most major towns and cities stateside) the other day and found a compact round stick of green buffing compound for just under $5. It’s a good sized stick about 20mm diameter and 10cm long. Enough for about ten years or more for anyone sharpening up every day. I used it for three days of demoing and found it to have good consistency and charges the leather strop appreciably. Some are to powdery and require the heat build up from a rotary machine mop to charge the rotating wheel.