For the keymap, type xev in a console. Then press a key and look at the output to see its keycode. Take that and edit /etc/X11/kb/Tosa/xmodmap_us. If the keycode isn't in the file, add it in the same format as the others. You can also change the functions of other keys there.
As for feeds, I think any pdaXrom feed should work as long as it is for the correct beta.