For the screen we can use: WINGONEER Raspberry Pi 3.5inch 800×480 60fps, which uses the GPIO. I think the documentation for this can be found in the raspi-wiki on this page. Assuming that this is the right display, then we need to write the following into the /boot/config.txt file.

#for raspberry pi 3b+/3b/2b+/b+
dtoverlay=dpi18
overscan_left=0
overscan_right=0
overscan_top=0
overscan_bottom=0
framebuffer_width=800
framebuffer_height=480
enable_dpi_lcd=1
display_default_lcd=1
dpi_group=2
dpi_mode=87
dpi_output_format=0x6f005
hdmi_timings=480 0 16 16 24 800 0 4 2 2 0 0 0 60 0 32000000 6
display_rotate=3

For the Battery I think we can use this UPS hat. Since it stacks, I think that means we can use a Raspberry Pi 3 (and underclock it down to match the Pi Zero), to get wifi and bluetooth. I don’t think we need the Raspberry Pi 3B+ or 4, since we generally don’t need the heat or extra power, since we’re generally going for 2d at 800×480.