I know where your coming from. I live in Ontario and the availability
of fish is basically first come first served.
I have developed a good rapport with the LFS here and he will hold a
fish for me for a good period of time if I choose.
I have also bought fish the day after they are brought in and do run a
risk of also bringing in something into my tank not welcome.
I have only done this a couple of times as the fish that were brought
in were one's that I hadn't had on order and also were one's that sold
fast.
A quarantine tank is really the only way to go in that case. This is
also something I don't have up and running either but is the next thing
on my "to do list". I have a lot of soft corals and I just can't take a
chance that my luck is going to hold out forever. (nice thought
but....."
HTH

-Soup