Style 68 wheel and tire questions

I have some Style 68 wheels:

http://www.bmwtips.com/tipsntricks/wheels/bmw_wheel_068.jpg

and needed to know two things:

1.) What size is the emblem on the center caps? I need to buy replacements for all four wheels. If you have suggestions on best place to buy that would be great.

2.) I currently had 225/45/17 around all four tires. I am in need of new ones and in my research I found that my car came with staggered tires. Front - 225/45/17 Rear - 245/40/17 So my question...

Style 68 wheel and tire questions