Originally Posted by
RubeRad
I'm surprised nobody has mentioned the alternative of using an old tube. Many cheap bikes I see, the rubber rim strip seems equivalent to inner tube anyways. You would probably want a tube from a wheel at least 1 size smaller so it would be snug. Use scissors or a razor to cut a strip all the way around, the desired width, maybe a little wider for an inch or so and then use a razor to carefully cut a hole for the valve.
Cheap bikes have single-wall rims so the strip is only preventing abrasion by nipple heads.
Better bikes have double-wall rims so the strip needs to be strong enough to resist tube incursion into the socket holes.