The way you can determine the charging state of your Apple Pencil is through your iPad Pro, itself. All you have to do is swipe down from the center of your screen and scroll left to the widgets screen. If you do not see the "batteries" charging widget, go to the bottom of the page and tap "edit widgets" and add the batteries widget so it appears. This widget should show you how charged your Pencil is as well as your iPad. It even shows when you have it currently connected, denoted by a tiny lightning bolt indicating it is charging when you have it plugged in. There is no indicator on the Apple Pencil itself, however.
ps- if you find a way to get a hold of that charging adapter, I, too, am interested in acquiring one as it is difficult always charging it through the bottom of my ipad.