For the record, the 3.5" 640x480 IPS screen is indeed being sold with a different AV/VGA driver board now, called PCB800855. eBay, AliExpress links
But like CrazyGadget said, the G-Boy is only designed to work with 3.5" sized driver boards. While you could potentially trim that driver board, the LCD ribbon may not line up with the connector and it won't work with the standard LCD bracket. It would be a very messy solution. Better to get the correct UT-HDMI035 driver board.
This is currently the cheapest listing on AliExpress ($35)