In addition to inner tubes, I buy rubber or vinyl tubing at the local hardware store by the foot. For example, you could buy a foot of 1" diameter, thin wall vinyl tubing. You can cut the tubing to length, then slit/trim the tubing to fit the required diameter. The cut tubing has a natural curl, so it tends to self-wrap. A foot maybe costs $1 at most, and it will last a long time! In fact, I have a handful of short pieces of tubing of varying diameter and wall thicknesses in my garage. Like innertubes, they do come in handy for all sorts or things around the house.