Yes, the Heavy butt cap is available. But what is weird is that I see it on mine. Can you try refreshing and clearing your cookies? Or could you send us a picture at firstname.lastname@example.org of what you are seeing?
Would be great if you guys posted a video of how to install the kit. Going over everything from changing the length, putting in the grommets, and installing the weighted cap. And go over what the total weight, swingweight, balance would be after these modifications.