An approx. 10cm long 12mm outer diameter aluminium pipe was milled to length and a 6mm diameter hole was milled in approx 10mm from one end:

Two end pieces, each with an 2mm hole and fitting to the inner diameter of the aluminium tube were machined on the lathe. One got an approx 5mm outer diameter (to fit 4mm inner diameter tubing), and another one got an luer lock to fit stainless steel cannula (available from China, 10pcs for <1Eur). It is possible to bend these stainless steel cannula by inserting 1mm diameter welding wire, heating the needle with a blow torch and carefully pulling the welding wire. This gives a nice bended cannula.