hey andrew, long time no see, hope all is well. Ritchie, from the old team Schuie days

Some brands just sell 1/8 tires with a smaller diameter special for pancars

Looks like Kimihiko is coming out with what you're looking for, just a few years later.

EPS-J Twelve Tire Processor (kimihiko-yano.jp)

watch some video from this product, looks nice, but seems removing the wheel from the arbor seems clumsy, not having much room, the design probably sets for small base footprint.
hearsay that this product is resell from a china mfy

You have the video link?

Cheers

will ping you for that

Lesser expensive (cheap)......i'd used a 3 Racing tire truer w/c used a hacksaw blade (trimmed down) to fit it's holder- it's pinched with a screw. The manner in w/c the cutter is oriented ( the cross tire truer ) seems to be the (obstacle) problem . What if a "cutter" is sourced from a different industry ; a machinist utilizes tooling to mill metals according to spec . Those tend to be pricey but the Stock (oem) type cutter according to the above pictures can be found to be discontinued - maybe try contacting someone such as a machinist. McMaster-Carr , Grainger , even Henry Schein maybe an on-line source.....good luck with your search.

https://www.youtube.com/watch?v=sHA_hYx8Zpk
https://www.youtube.com/watch?v=cpbSJ6fycaE

There's a industrial company called A1 lazer just down the street that can cut foam tires. Find a lazer place near.you. I gave a1 lazer contact tire 35 and 40 shore over a year ago. He sent to a lab to have tested so he could source similar foam.