I took a chance and bought these - laudation 36V 10ah Li-ion Battery 18650 (10s3p) for $135 shipped
https://www.ebay.com/itm/laudation-36V-10ah-Li-ion-Battery-18650-Rechargeable-battery-for-E-Bike-Electric/254277288980?ssPageName=STRK%3AMEBIDX%3AIT&_trksid=p2057872.m2749.l2649
(they have changed this link to be either Samsun or Panasonic batteries since I bought it, so who knows what you will see with that link).
It is supposed to have Built-in Panasonic NCR18650BD batteries. Advertised as such, and confirmed by vendor.
Although the batteries are the right "color" they are unmarked, so I'm doubtful that is what they are. Certainly doesn't have the tel-tail black stripes at the ends of the cells.
I'm using this on a tiny controller (max 12 amps, probably 10 continuous), but the battery got hot after running hard for an hour - which doesn't sound right (although I had insulation around it as padding - I can't do that, so now it can breathe better). Its rated 15amp continuous. It did give me about 1hr 15min run time which is is what I expect.
The wiring is flimsy - not what I am used to at all. I did swap out the connectors to something more reliable (XT90). Cells are wrapped in cardboard - not really expecting more at this price point.
Its a nice size, nice and light (3.75lbs), and easily fits in a frame bag under my top tube.
Oddly, they sent me a charger even though it was not supposed to be included.
My Battery:
As advertized on ebay: