Got mine from Price Angels. They had some other stuff I wanted at the same time that no one else I know of who carry's flash carts had.
They're pretty typical for a DX like stare. Takes a few days minimum before your stuff ships as they round it up from the suppliers and in some cases much longer. MY DS2 shipped quickly though, had it within a couple weeks of ordering it.
If you want it quicker and are willing to pay a bit more Gamer Section, Kick Gaming and Real Hot Stuff are reputable shops that are North American based.