Well. i had 2 misprinted ED 209 legs and a body from my attempts at making my own ED.
and then the panzer zug print showed up.
And in my best gru voice: LIGHTBULB!
Here is a gear krieg inspired panzer 4 walker/pod! The gun is a 1:350 scale 46/45 Yamato cannon in aluminium (which i also had lying around

Stop ED 209 torso print before you reach the armour cowling. you want the engine only
Stop ED 209 leg print just above the knee join. If you wish to recreate the walking pose I've used, allow one print to continue approximately 5 MM higher.
Make certain to both Support and Raft the zug half, as this will give you a surface to attach the legs
Scale your iron cross to a suitable size for your base.

Assembly:
the Bottom section of the ED 209 engine glues to the rear of your armoured box.
when glueing the legs, glue the longer leg further back on the (still intact.. you did keep it intact didn't you?) raft. this gives you the forward stepping pose.

If you are not an insane modeller, and do not keep a collection of turned barrels handy for projects, you could use a styrene rod, a chopstick, a brass tube, or hell, there's panzer barrels on thingiverse, find one and print it yourself.