Mounted cavalry arms or firearms?

[incinerator950]

So I'm about to get a Khorneate Lord with an axe on a Juggernaut, and I'm having difficulty finding the last piece of my model, which is the left arm.

 

I'm using a templar power axe in the right arm, and have to now acquire a new arm for the left hand as I am out of appropriate bits (short of mutations which I don't want). I am not familiar with cavalry models, and I was wondering what can I sub in as I can just holster the Warlord's sidearm in a holster as opposed to riding a moving machine with two weapons.

[Lucio]

A Space Marine boltgun arm, with the hand cut off at the wrist and twisted 180 degrees should give you something to position as if gripling the pommel of the saddle, though you may need to also cut and bend at the elbow.

 

To help with the positioning, use greenstuff with a little more yellow in the mix to give you time to line things up in a natural pose.