I'm located in the U.S. i'm having trouble finding this or something similar from other brands. The ones i have found are about $20 for something that i figured shouldn't be that difficult. Could i just use a spare fitting & extra tubing to create my own inlet tube? I'm using EK's multiport top, do you know if the inside of this cap uses G1/4 threads?
Theoretically yes but you want to make sure you don't use EKWB's fitting inside the res since the compression ring around it is aluminum, having that in contact with the fluid would not be good.
As for options within the US performance PC and others carry this part.