You should be able to flash with any supported firmware for that particular model, and i assume those are still available from the maker.
I am not familiar with the brand myself, but normally the firmware file are called something .bin
So that .bin file you but on a empty memory card, if that card are 32GB or less no problem, if your card are a larger model it most likely need to be formatted in the camera.
32 GB cards ans smaller are formatted by a PC in FAT 32 which most cameras need, but larger memory cards a PC will format to Ext FAT
If you have a larger card and it have been in the camera, you can try and look at its properties it should then figure as FAT 32, if that is the case you can put the .bin firmware file on the memory card, and the camera should then update when you power it on with that memory card in the camera ( often a LED will flash fast while the flash go on, after that the camera will reboot and start recording wit the default values.
You should also be able to use any old memory card, i often use old 8 and 16 GB memory cards ( SDHC ) and i have yet to experience a camera that dont work in.
If you have a larger memory card and it is exfat, then there are also some software that can format it to fat32 instead, but ill be damned if i can remember the name of that software right now.
In some cases often seen with Ambraella based cameras if the camera is "bricked" you need to load a new firmware with the camera commented to a PC and using a little software called USB direct, and not least a firmware file that are named something .elf.
The correct .elf file are a must have as USB direct are not meant for using the regular .bin firmwares.
I sort of fear you are needing to go the USB direct route, but then you need the .elf file to re-flash with, and those also have to be for the particular model of camera so usually you get those from the maker too.