I've bought several genuine DG2813s from allwatchparts.com

http://allwatchparts.com/-Chinese-Automatic-DG2813-Mechanical-Movement_p_925.html

I can't promise that they only sell real "Five Goats" movements, but out of 6 I've purchased across a month and a half, all have been real DGs.

As for whether these are decent movements or not...I'm not experienced enough to really say for sure. I will say that I've taken an old one apart and I don't see anything wrong with it. The components were all well made and the overall design seems sound. It is very similar to a seagull ST16, which is known to be a solid movement. Some people say the 2813s are okay movements, other people say they are utter garbage. These are cheap enough that you can get one and decide for yourself. It will work with the hands and dials for a Miyota 8215.

I ended up buying the first one to replace the movement in a Rotary watch I've had for about 10 years. Its DG movement ran great for 10 years before gumming up. The rest have been movements for experiments.

Yes there's a big difference. Get the 2836