firmware on these older players can not be extracted, if it could then maybe we would not have so many dead onda clone players
the only possible way to find a firm for your players is to take it apart and gather as many board ID numbers as possible, the try and search placers like
http://www.s1fw.com/ to see if anyone has possibly found a firmware
this is a big risk, even if the numbers seem to match it is no guarantees, also taking apart the player can be fiddly, just watch for the battery wires and the speaker wires as they are easily pulled lose from their solder
number in the player info screen mean nothing, firmware number mean nothing and the look of the player means nothing, taking apart and noting the numbers is the only possible way, and then there is no definite
if you like to mess about then give it a go, i have player many a time and also killed several players!!!