I was watching some of Dr. Ashen's Popstation reviews and noticed that several of them had ZC in their IDs. Googling "ZC-2032" (the ID of the
Game & Radio) brpught me to
this Tradeee page, which mentions Dongguan Caltime Electronics Co., Ltd. Googling Caltime's name brought me to
their official site which does sell some LCD games, but disappointingly no Popstations. I went back to
their tradeee page, clicked on the product list, browsed around, and I found info on lots of Popstations they made, confirming them as one of many Popstation manufacturers.
EDIT: I think I found the manufacturers of Retieval Mankind's Batman and PSP Onling. Googling their respecive IDs (XY-930 and AX-688) led me to
ToysBaba and
EC21 listings for each game. RMB is made by
Jiangyun Toys and PSP Onling is made by
HK Aixin Electronics Co., Ltd.