Together with a friend of mine we conjured up this solution:
They are 3D printed inserts that use DEX210 imperial size axles, but I use them with TRF wheels on DEX210 metric size axles. I also measured it for you with DEX210 rims for you using wide mounted Schumacher Minispikes:
As you can see it's a close call, but it should work just fine. Also, I want to note my left wheel is showing a bit of excessive negative camber, which is causing the car to be a bit wider than it should be.
The insert set included pieces to use 2, 3 and 4mm trailing just like the standard wheel axle setup and it costs EU8.50 (+/-GBP6.65). PM me if you need any more info
Also, if you really require a car that's safely within the regulations, I am considering to make one-piece steering arms (no inserts), so I can make the car safely within the 250mm for all wheel and tire combinations.