Short answer : Solder some leads to the battery terminals, add a diode so your external battery does not get charged by the motherboard and solder in a CR-2032 battery holder into which you can install the proper battery . If your board needs more than 3V to be happy, this will not work .

Disclosing
a) what battery the board originally used
b) what the board's brand and model are
would be helpful .

At last check, nobody here is a mind reader . 😉

You need a standard 4-pin "2.54mm single row pin header". You can often find them in sizes of 20 to 50 pins that are timmable between pins to break them into the desired size. You should be able to get that part at every reputable electronics store, Google is full of matching results once you know the correct name for that part.