You can get the MAS3507D processor from
Spectre Online.
They were £20 + Postage (approx £6 in the UK) when I enquired about the chip waaaaay back in September. Buying the A600 with a memory upgrade, adding a HD and finding out about the chip was about as far as I got with my A600 in car project thing. I struggled to find a good source of smallish TFT screens for a reasonable price. If anyone knows of any good sources please let me know!
Thanks
Kev