You can define shortcuts for that:

    nth=1; wmctrl -i -a $( wmctrl -l | awk '$2 == "0" { print $1 }' | sed -n "${nth}p" )

I guess you would need 9 shortcuts and you would set nth to the number associated with that shortcut. Works for me at least. You might have to define the shortcut to "bash -c " followed by the above oneliner with some appropriate quoting and escaping of inner quotes.