Try Tob Knobs and Restoration Hardware.

I bought my knobs and pulls from www.hardwarehut.com. I got the cliffside industries artisan series in matte black. They are solid brass and feel really solid. Good luck! Restoration Hardware has a lot of options too if you are okay with oil rubbed bronze.

Coolknobsandpulls.com was organized in a way so that you could see what sizes were available with each style.

I understand your frustration, this is what drove me nuts!

Their prices were also very good.

Here is a link that might be useful: cool knobs and pulls

I purchased mine at Lee Valley Hardware. They have a large selection at very reasonable prices.

Here is a link that might be useful: Lee Valley Hardware