If it were me, I’d snip the four cores and re-join them. You can get a special tool to remove the pins from plugs like that – look on ebay – but it’s going to be hard to be sure if you’ve got it right or if it’ll work.
You might be able to get compatible connectors on the internet somewhere, but without the proper crimping tools it’ll be more faff than simply breaking and rejoining the wire.
Warning though – if that’s connected to a battery you have to be incredibly careful because snipping them all together will short the battery out – and then having dangling bare wires around could also create shorts. And if it’s a Li-ion battery and you short it out you’ll trip the protection circuit and ruin it.