teflon tubes I get from amazon.
few bucks for 2 metres. should be 4mm outer diameter and 2mm inner diameter.
If you don't already have a digital caliper - get one :-)
Pretty much an essential for any 3d printing.
https://www.amazon.com/Staron-Electr...gital+calipers
no idea whether that's a genuine price - but for 99c got to be worth a punt :-)