Bios flash

Hello, I recently purchased a used Lenovo Ideacenter b540p and there is an issue with the system, on boot up I get the error:
error 00ce machine type and serial number are invalid, I know how to fix this with a bios flash, I can’t seem to find a copy of the original bios, if anyone knows where I can get a copy of it, that would be great, as Lenovo does not provide a copy of the original or an update on their web site, any help is appreciated.
Thanks.