Need to change workout routine, any Abs exercise?

there is not much you can do while standing up
however there is one thing i like to do that doesnt involve laying on my back that i think would be good.
i call them seated trunk rotations
basically, get a heavy object, preferably a medicine ball, a free weight will work just as well.
now sit down and so your but and feet are touching the ground and nothing else.
now try to balance on your tail bone with your feet in the air and your back at a 45% angle from the floor.
then you take the weight and rotate your trunk (torso) right and left and with each rotation, you touch the weight to the ground very lightly.
remember your feet should never touch the floor

if you find that is too easy for you to do and you have a work out partner try this one…

have your partner stand up a few feet in front of you
you get on the floor into the balancing on your tail bone position.
have your partner take a medicine ball (or a basketball will work but its better to have a heavy ball) and throw it to one of your side
you then catch the ball and do a seated trunk rotation before tossing it back to your partner.
once again your feet should never touch the floor

i hope this helps