Freshwater drain replacement

Hi,
I have a 2017 Fairford and the freshwater drain has been lost. I know I need a drain tap, two hose clips and some blue convoluted hose. What length of hose should I order. Grateful for some assistance please.

Sold by the  metre which is probably  plenty by AS spares or CakTanks.

Thanks Paulmold I saw that on the AS spares page but did not want to get too much or too little. Is it easy to cut and trim.
Ta