Anything at all that will form an airtight seal and survive the wear and tear.
Nylon is fine for instance. You don't need a large bore diameter.
That clear plastic tubing they use for brake fluid would work well, for instance, the cheaper flexible stuff. Use the matching brass fittings are the Dynon end, and AN fittings + brass fittings at the pitot end. That is one suggestion. Or just use softer hose with hose clamps, that works 100% fine too.