I had it made up for me at an marine/automotive store, was quite expensive. The hose they used was
fuel line hose, I think the same hose that goes to the
fuel pump on my diesel. It's quite thick walled and able to take the required pressure. Go to your local chandler and check out the hoses, take the fitting with you as you'll need to be sure to get the correct inside diameter hose. For what it's worth, before you spend any serious money on your pressurized
stove, you should be comfortable that it's worth it. I wasted a couple of hundred on mine before giving up the ghost, and am really glad I now have a non pressurized unit (an Origo 6000 bought on ebay for 800). It's a pain that
stoves (and fridges) are so expensive, but you'll only spend the money once, and get peace of mind and reliable service for many years.
All the best