I know that the 225/40/19 was an optional tyre on the M3 (front). You can get them in heaps of brands - price varies fm 230 - 700. I don't know about the 235, however, I saw a New Alfa 159 today with 235/40/19 P Zero's, So I think there is some tyres in it, I think yokohama do one too.
I hate tyres. It takes so much shopping/time to get a GOOD tyre at a GOOD price