As for stock ROMs for Coby devices, there aren't any from Coby and there never will be. Coby has been out of business for a few years now. There are also no system dumps for your device, which means no way to restore your tablet, with the possible exception of a factory reset.
Your device is likely one of the later units Coby released with a nand lock on it. Installing a custom recovery or custom ROM will trip the nand lock and render the internal storage useless. Try a custom ROM since you have little to lose anyway, but be aware of the possible outcome.