Best place to buy inner tubes

where is the best place to buy inner tubes in usa or online? i need 8 inch ones to replace on my trampa board. i tried a couple hardware stores, home depot, target. i also tried harbor freight but their 8" tube was a different size then what i needed. this kind of makes me fearful to order online and i dont want to order directly from trampa because shipping over the pond.

any recommendations would be greatly appreciated! thanks

on the tyre should be the name for it like size and width google that and you should find it somewhere

Plenty of 200 x 50 tubes on ebay. Scooter version will do.