Enduro tubes, or also cut the old tube down the middle, and wrap it around the new tube. Then gooi slime in, just doing it with my little stroker now and the one I hear works best is this Amerseal tyre sealant "ultimate premium heavy duty" (sounds chinese innit, but its American made)
32 oz for R80, and you need about 10oz-15oz per wheel on a motorcycle.
I got a few bottles at Suzuki Toy Store in Centurion.