Finally the FlashROM 512kb cartridge boards arrived. These boards are based on original Eric Boez's design and were reworked for more flexibility. The type of ASCII mapper (8 or 16 bit) can be set with a selection of jumpers, there's also an option to use normal capacitors instead of tantal ones. Here's the picture of the board:
I have 6 boards available for sale. I can also provide the address of the LZ93A13 mapper chip's supplier as I am not going to sell those chips myself. The board costs 4 euros with 2 to 4 euro shipment within EU depending how many boards is in the package. Please contact me if you are interested to purchase these boards.
but all are needed to set either 8 bit or 16 bit mapper mode. So you can use one cartridge in 2 different modes. 
