I have been playing one for several months now, a beautiful instrument I must say.
You're best chance at finding one would be online depending where you are really try kijiji, ebay or even local selling/buying/trading sites.
I bought mine for $700 but depending what kind of accordion you want, bigger keys usually cheaper as well as kids accordions (these are really fun and can be easily portable for your rough adventures)
To summarize;
-Online sites or (local sites)
-Ask around, friends, family, neighbours, whoever
-Grandparents dead or alive, the G's are highly more likely to have them for some reason
Also most music stores don't normally carry this rare and wonderful instrument sadly to say but there are actual stores out there that just specialize in Accordions.
finding some in Thrifts are possible as well, good luck!