You can find it at the following URL
support.micronic.cz/pub/pub/boardy/zidabios/4dps/4dps_400.arj. JUST NOTE IMPORTANT THINGS
1. This is not a flash update. It should be programmed on a NEW EPROM(i.e. 27C010A)! DO NOT ERASE YOUR OLD ONE! In few cases this upgrade DO NOT work and you SHOULD HAVE THE ORIGINAL BIOS if the new one does not work. And please answer me if it helps you and if you found something another as a BIOS upgrade.