Treadmill desk has worked for me so far
If you have a standing desk already you just need a treadmill
I worried before I bought the treadmill that I would be too un-stable to use a computer but that isn't the case it works no problem I run the treadmill at slowest speed but I can work at higher speeds too
It's also nice to get out the house so if you can fit in a chore like take the rubbish out that'll help wake you up a bit in the mornings