Reddit mentions of Bell Solid Tube NoMorFlat Bicycle Inner Tire Tube 26 x 1.75-1.95

How about using a solid tube in a standard tire? Here's one:

http://www.amazon.com/Bell-Solid-NoMorFlat-Bicycle-1-75-1-95/dp/B000BOCA44

You could likely cut up a couple of them to fit into a 29" tire.

No problem! And I suggest switching out the tubes inside them with a foam one like this https://www.amazon.com/gp/product/B000BOCA44/ref=oh_aui_detailpage_o01_s00?ie=UTF8&psc=1

You only need one, and can cut it in half and it will fit perfectly in your tires replacing your tube. They're super dense and hard, they roll beautifully and you'll never need to replace them. You'll only need to cover the hole where the valve goes on the rim to prevent water from getting in there.

Ugh, those are the worst. I used to try putting a protective layer on my tires and used the slime inner tubes. It usually worked, but still not always.

Since then, I have discovered airless inner tubes. They are the devil to put on, they are stiff, and they are heavier than air inner tubes (but about the same weight as the slime inner tubes plus a plastic layer). But you'll never have to inflate your tire again, and you won't have to change them until you need to replace your tire.

For me, it was worth the switch.

https://www.amazon.com/dp/B000BOCA44/ref=twister_B01HY12VOU?_encoding=UTF8&psc=1