Wow... That's a real pain.
First things first: originally, from where did the computer came? You are describing a BIOS lock out feature that most people don't use, unless when dealing with highly sensitive information contained within. Or suffering from a serious case of paranoia.
BIOS lock out function is put in place to assure that, in the case of a computer is stolen, no one can access the machine. And I seriously doubt that removing the CMOS battery will do any good.
Removing the battery, specially when considering these very small machines, involves taking apart the whole thing to reach it. Here is a video for the process, if you feel brave enough for it.
Another option is to try to force the machine to give you a backdoor password.
1) Start by removing the battery and connect the computer directly to the power source.
2) When the computer prompts for the password, take a few guesses. At some point, it will give a message of "System Disabled" and a code, that can be made up of number, letter or both. Write it down on a piece of paper. Be very careful to correctly read the code: do not mistake a letter for a number or vice-verse.
Do not worry about the "System disabled" message: this is a scare tactic. Pull the plug on the computer, give it a minute to "breathe" without any power coursing through its circuits and then reconnect the power cable. It will run.
3) Go to this site: https://bios-pw.org/#
This is not malware. This site was created using reverse engineering to create a tool to generate passwords to unlock machines like your. Insert the code you wrote down and get a password. Write it down and insert it on the locked computer. Hopefully, you'll get in.
Next step is to go into the BIOS and disable the thing!
Try this and drop a line here. We'll see what we can do if none of this works.