Can you measure the Scottoiler connector you're removing?
I rejoined mine on my 650 (properly, it had a screw in the 3 way before) and it took a 4mm barbed joiner, £1.50 on eBay. I tried a 6, and although I probably could have made it fit, the 4mm was the correct size.
A search for "STRAIGHT Reducer JOINER TUBING PLASTIC BARBED CONNECTOR" should find you something suitable