I've had great fittings at Nordstrom, believe it or not. They have trained bra fitters there.
It's best to do a braless fitting for most accurate results, but my fitter was careful to make sure I was comfortable with it. You could always ask.
If you don't want to hit up a big department store, you could also check for local lingerie shops. They should all do fittings as well.
Remember that every bra brand fits differently, so even if you end up, say, a 36C, that doesn't mean you'll wear that size in every brand. A good fitter will talk to you about what style of bra you feel most comfortable in and will make sure you have plenty of options in the right sizes. She'll show you how to know when your bra fits well/poorly.
In case you can't tell, I'm a huge believer in bra fittings! Ha.