I always carry a spare tube even though I run tubeless. I've cut my sidewall on a rock and so has a friend I've been with and neither of which the Stan's goo could handle, had to boot em and tube em . Anyway if you don't want to go with a backpack or a saddle bag you can velcro or tape one under your seat or to the frame somewhere. And like frankenmike if the 29er tube is too bulky you can go with a 26er or 27.5er tube and just stretch it. Still have to throw a pump/co2 carts in a pocket or something though.