What I use are "Shurflo" marine water fittings , cheap to buy , food grade , and they screw on to a standard 1/2" BSP nipple with a wingnut type thingy.
They are barded at on end to take 1/2" tubing , I did fit a 20c "O" ring inside each to make them seal better.
They work really well.
link to whitworths and the fitting below , if you click on the 1/2" elbow one there is a pic. Thier inline filters are good too ,$11.95