I don't have any problems getting cycling clothes to fit me; that is if they carry x-smalls in a particular brand. I have had some "styles" of jerseys not fit well, or shorts that have the wrong kind of chamois, but not really fit. There's been a few PI things I liked, but PI does not make cycling clothes for women in my size, or at least most distributors don't carry them. Shebeest tops are generally too big for me, but I love the shorts. I think you need to look very carefully at the manufacturer's size charts, as they could be very different.
My problem is with regular clothes. Vanity sizing and the lengthening of petite sized pants is an issue. Petite pants used to be 28.5 or 29 inches. Now they are 30 inches, and even with heels, that's too long for me. And I don't like the longer style t shirts. Even in a petite xx-small, some are too long. I feel like the market is not catering at all to short people!