I find it highly unlikely there is any other bios to find. Emachines is a joint venture between TriGem computers and KDS. I would expect the motherboard would be a TriGem creation specific to the particular Emachine in question. I do not believe TriGem sells motherboards alone, if they do I have not encountered them. Unfortunately the fact that you wish for another bios does not incline it to exist.
It's no great loss in any event, if your celeron is the elder Mendocino core 533 it is near its limits at 533 anyway, and there is likely little in the way of overclocking features present in the motherboard for a bios to command. Unless you do pin modifications for both fsb and vcore I doubt that there is any overclocking the machine, and the results if accomplished would be slight enough to make the effort seem excessive.
Looking at the site suggested above, your motherboard is indeed a TriGem creation, called the Anaheim2. This is a i810 chipset board, but the big question is the cpu. If it is a 533a (celemine) core it might just run at 100fsb, many did. At most it would take a mild vcore increase. If it is the older 533, I wouldn't even bother.
