I to wanted 225/40-17 because is the perfect change from stock 205/55/15, but i didn't had any luck, i went with 235/40-17 from falken. That is the best i could do.
Now i'm in the same hellhole as you with the rear tires i was looking for 255/35/17 but i can't find nowhere and again only FALKEN has 245/35/17 for my 17x8 wheels.
And i know stock is 195/60-15
