Bought on eBay. Quick search shows this item to be probably the same thing I bought:
https://www.ebay.com/itm/4X-20mm-Lon...W/391317052501
Of course that link will eventually go dead, so this is the title: 4X 20mm Long Shaft Car Door Lock Actuator For Mabuchi Lexus Toyota Honda 12V NEW
Note that it says "For Mabuchi" vs. just "Mabuchi", so it is a Chinese clone. When my 4 arrived, I did a quick test, applying 12V and they all worked fine. They also matched up in size and polarity with the short-shaft ones I have.
But I have not installed them in anything yet. Due to the incredibly low price (4 for $10, 10 for $20), I did not research too much and just bought them to stick on the shelf.
Also, from looking at that eBay listing, it contains the same part number as the short-shaft motors, but with an extra L (for long shaft, I will assume) at the end. So searching for that may be your best bet:
FC-280PC-22125L
Also, it looks like there are some of these motors available with a flat shaft. From my photos of the driver's door lock actuator, the shaft is round, not flat.