One way to go would be to build your own version of ps with all the options you need using the source code of procps
There is more information on this here busybox - how to enable ps -ux option on busy box - Stack Overflow
Also, take a look at BusyBox - The Swiss Army Knife of Embedded Linux
I was successful in compiling procps 3.8.2 from source on 3.10.17-poky-edison.
1. Download procps source from http://procps.sourceforge.net/download.html
2. Get procps 3.8.2 patches from http://www.linuxfromscratch.org/lfs/view/7.1/chapter03/patches.html
3. Follow instructions at http://www.linuxfromscratch.org/lfs/view/7.2/chapter06/procps.html
(Note: you'll need to first add the repos and "opkg install coreutils")