I can't think of any part that would be cheaper than replacement shoes other than a glow plug. Maybe fuel line at a buck a foot.
https://www.ebay.com/itm/Traxxas-T-Maxx-Revo-2-5-3-3-Replacement-Clutch-Shoes-Springs-4146X-/310879938960
You make it seem as though the clutch shoes break constantly. One broke. Again, it happens. If you think nothing should ever break when we run our rigs you'll be sorely disappointed. You won't be the first one who ever changed the tire size, so that's not the issue. There really is no...
My first RC was the Traxxas Tmaxx. It ran almost daily and it ran hard in all conditions. I never had a clutch shoe break or even wear out in the time I had it. I'm just saying, it happens but that doesn't mean it's a defect or a problem. It broke. No biggie, just get a new pair of shoes...