I tried the lance thing on my
SM bike sgt and the arms are just to off scale and i was way to lazy to wrap them in greenstuff and or cut off the lance to put it on another arm.
You could try using one of the Grey Knight's that isn't in
TDA or you can buy a britonian knights box and mod that.
As for bitz the only place that i can find to get them from is thewarstore.com and the bitz link is here
http://thewarstore.com/battlewagonbits.html