I would assume that the Kobo Wifi is a Netronix E60820.
If so, what other devices have the same hardware base? Any ideas?

Here's the meager info Netronix gives about the device:
http://www.netronixinc.com/E60800.html

[edit] It seems there's another eReader, called "Green book" that also uses this hardware.

Yes, Greenbook Inc. is a subsidiary of Netronix and they sold many EB600 ereaders in Taiwan. I've just bought a new "EzRead Touch wifi (special offer)" for about US$96 and like it a lot. The one you just mentioned was sold out in Taiwan already.

E60820, E60822(wifi): (sold out both)
http://www.ezread.com.tw/hardware_info/精靈180白
http://www.ezread.com.tw/hardware_info/魔力182

EzRead Touch (wifi) - Special Offer: (with ad during power on/off)
http://www.ezread.com.tw/hardware_info/EZRead%20Touch%20Special%20Offer