a range rod. Its not one that attaches to the gun, but you take it with you shooting. I really like the CVA plastic one that costs about 12 bucks. you can bend it like an ugly stik and its tough as nails. comes with a couple attachments too. if its too long, just cut it down a bit.
patches
powder measure
funnel
a good rest
primers
bullets and/or sabots
spare breechplug maybe