First, the shop that told you that they couldn't do a rear wheel alignment is wrong. What they probably meant was that there was no factory built in adjustability - AND they refuse to takes the steps needed to allow for adjustability. Put another way, they were just too lazy to take the steps needed to do a rear wheel alignment. Please take note that doing a rear wheel alignment MIGHT require shims or eccentric bolts or a strut plate to get the needed adjustability - and that means more cost to you - but it can be done.