The 303 either comes in 3" or 2 3/4", it will not shoot both reliably if it is a 3" gun.
You may be SOL trying to find 2 3/4" 20ga turkey loads locally. Your best bet is to find the 5 round boxes and buy a few different brands and shot sizes to pattern. This way you will find that sweet spot load your gun really likes and not be stuck with a few boxes of a particular load that do not pattern well.
