yes, Frame Destinations are a good source. I have purchased from him before. I buy full sheets of mat and mountboard from Dick Blick Art Supply, and cut my own. And I am now chopping and joining my own frames, so that I can make my frames and matboard to the size the picture requires, instead of the other way around.
I am kind of unhappy with my present frame stock supplier and would like to find a better source for full length stock.