I'm in the middle of an engine and box swap on my rst. The box I bought is a rebuilt turbo diesel item. I had to chop a bit of the casing with the grinder to get the ABS pumps to bolt on, and have now discovered I have a spare plug on my loom (think it's for the reverse lights) and nowhere on the box to plug it into

the plug is roundish with a 2 pin connector iirc
How can I get round this?