If your model requires the special fluid from Volvo, I wouldn't even try to use anything else. This OEM fluid is probably at least semi-synthetic.
If you are handy, then get the fluid from the dealer and do it yourself. Otherwise, let the dealer do it.
It is unlikely that the local quicklube shops would have the Volvo fluid unless you made arrangements ahead of time. Same with most shops that have the flush machines.

Sure, the special fluid is pricey. But transmissions aren't exactly cheap, and I regard the change as being inexpensive insurance.