Only with the other base parts. As you can imagine, the tread set is the most expensive part (other than the motors), and besides, it is not easy to work up the alignments for a treaded drive system. For people that want some cheap rubber treads there are those 1/24-scale tank toys available.
ABS is usually a hard plastic. The treads on the Tracked Drive units are hard ABS, and the XL treads are rubber. I'm not sure what the rubber composition is on the Tankbot XL treads, but it's probably butyl-based, so it's all in the family.
A little bit of looseness is fine, but maybe tighten the screw against the lock nut a little more. Tighten it so that it "locks," then back off just slightly. There should be only a very modest amount of play there. Once you get it set it will stay there permanently. The lock nuts are very agressive. I just measured the play in my picture prototype and if it's 1/2mm I'd be surprised!
Some new designs coming down the pike allow for using the axles (cut down) with the supplied retainer caps and some Dura collars. Of course, eight Dura collars adds a couple more bucks to the price, and you remember the name of my business... The play seems about the same, though, because the hole in the idler is a bit oversizedThis is why I use those small washers in the idlers.
That should work for at least a while, though super glue doesn't like mechanical stress this way. A compliant adhesive like silicone sealant might be better if these joints give out. But they probably never will anyway.
They are soft rubber, but maybe not quite as soft as the Tamiya treads.
-- Gordon