Mostly likely you missed the news recently announced by Richard Hutchinson on his latest creation, the FlashBoy Plus. Unlike the original, this new flash cart includes an internal save battery.
Yes, there is a Virtual Boy flash cart.
The upgrade marks the end of the original FlashBoy, which will no longer be produced. The last ever created is number two hundred and eighty four, which was meant to be the main prize for the PVB Coding Competition 2010. Since the the winner will now receive a FlashBoy Plus instead, the last flash cart is being auctioned off.
(Thanks Evan & Chris!)