Pressure washer - Challenge (Argos) DW-1800BH?

Looking for a part for Challenge DW-1800BH pressure washer from Argos.

The lance is leaking (still works but I'm getting soaked).

Inside the lance there is a plastic (stupid idea) part that the inlet hose feeds into, and it feeds out via the trigger.

The plastic part has a hairline crack along the "seam".

Looks a real easy fix but I cannot locate this part despite hours of trawling on tinterweb.

Anybody know where I can buy this part?

Thanks.