[pieter]

What I would love is something that can give alternative tube sizes.

My bike uses 22x3 tubes, which are unusual and hard to come by. However, there have been reports of 20x4 bike tubes or 18x3 motorcycle tubes also fitting.

A website that recommends more widely available or cheaper “this will also fit” tubes would be amazing.

[PascLeRasc]

What are those numbers in reference to? And what size tire do you have? Tubes can stretch to around 3x the size of a tire. A lot of enduro riders carry a 26" tube for their 29er to save some hip pack space.

[moasda]

You are right, my tube page also doesn't list a fitting tube for that size right now.