Here are the perfect sizes:
338x26 rotors for the front.
ECS
http://www.ecstuning.com/BMW-E82-135...ors/ES2550968/
OEM
http://www.ecstuning.com/BMW-E82-135...ors/ES2102485/
There are other aftermarket brands that carry them, you can choose from drilled, slotted or cross drilled.
For the rear 324x22
I have tried the ones that BMW makes for 135 but they won't fit 3 series. Why? I am not sure, the mechanic told me that the brake shoe is different. You will loose the handbrake if you do the swap.
IMO, the best bet is to find a similar size or one close to 324x22 that is made for 3 series. maybe 320x22 or 325x25.
I am using Zimmermann 300x20 now. Because i bought them brand new, i want to use them for a while first, until the fronts need to be changed, then i will change all four corners (which should be after this summer).
When i change the four corners, i will try 325x25 for the rears to see if they work.
http://www.ecstuning.com/Search/Rotors/ES1892428/
IF ANYONE IS WILLING TO GIVE THEM A TRY BEFORE ME, PLEASE CONFIRM FITMENT ON THIS POST.