Any doctor can order Ambry testing... there is a kit that can be done at any lab that comes with the necessary paperwork and vial (it's a standard vial that any lab already has and uses routinely.) So even your child's pediatrician can order this if there is delay in getting in somewhere else.
You can also post to Steve in the Ambry thread (Steve is with Ambry and posts there regularly to help us with our questions about testing, etc) to ask about this and he can tell you more about how exactly your child's ped. can 1/ work with insurance to get this covered and 2/ get the test kit, which you bring with you to the lab. <a target=_blank class=ftalternatingbarlinklarge href="http://www.cysticfibrosis.com/forums/messageview.cfm?catid=6&threadid=12677&enterthread=y">Ambry thread</a>