Sorry hun :) No pet store is going to have Burmese. Mink, yes, but no Burmese. Those just got imported from the UK just recently. Plain Jane agouti hoodeds will always be my favorite. My first rat was my soul-rat(takes part of your heart when they go) and she was an agouti hooded from Petco.
And a Trio of girls is always a good thing, especially if one passes away, the remaining one will still have a buddy and won't be lonely.