I have been able to use normal tack on arabs and arab crosses. What are you looking for? Saddle, bridles, halters, bits? If you have to order from somewhere, often if they don't have an actual 'arab' size, the small cob sizes work well for Arabs. Halter wise, if she has a really petite head, normal sized yearling halters fit well. If you can't find something specifically for Arabs you can always 'improvise' using other sized ones. Western bridles I've never had an issue fitting to a smaller head, because alot of them are designed to go smaller.
"The ideal horseman has the courage of a lion, the patience of a saint, and the hands of a woman..."