Sorry I don't know where to get hydraulic stuff for cheap but I did find this build. It's a Menzi-muck in 1:15 scale which is a very similar to the Kaiser. It might give you some ideas.
Video:
https://www.youtube.com/watch?v=Bxgw2R77GYo
Build thread (French speaking forum just run it through Google translate)
http://camions-rc.fr/forum/viewtopic.php?f=235&t=24474
Hope this helps...