The Axe is Autococker threads so most of the Barrel sets you see for sale here will fit it. On our team we have 16 Axe and run different kits. We have the following which all work really well with the Axe;
Sniper (I think)
Basically Any A/C will fit.
There is a new Super Freak kit made by Empire thats coming out soon which is meant to be the dogs danglies, but have not used this and so cannot comment on this.