I did a similar mod to an '88 Bronco I had, though I did it while upgrading to a 160A alternator to keep from burning the truck to the ground.
I ended up "rolling my own" battery cables and grounds with 1/0 welding cable, an assortment of lugs and terminals, solder pellets, and adhesive-lined heat shrink.
IMO, it ended up being much better than anything off-the-shelf, because it allowed me to re-route the cables in more sensible ways. Plus it only cost me about $100 in parts and supplies.
Find a local welding supply shop -- they should be able to hook you up with everything you need. The only tools needed are heavy-duty wire/cable cutters (I used bolt cutters) and a propane torch (to melt the solder and shrink the heat shrink). You could use a heat gun for the heat shrink, but the torch works just fine if you're careful.
2013 Billet Silver JKU Sport S, 6-Speed, TF Leveling Kit, Spidertrax 1.5" Spacers, 285/70R17 Firestone Destination M/Ts on OEM Sport wheels.