The funnel you can get from TDCMFG.com. The funnel by itself is not useful for revolvers and without the extension its hard for a rifle also, I only added the extra length, just kind of made sense, could not understand why they didn't do it in the first place. I've thought about sending them a letter, it is a US based company. They make another funnel with a threaded fitting and extension for loading flasks with. They just need to combine the two ideas.
The 25-20 SS cartridge case works out perfect for the task, of course this is a rare obsolete cartridge so not everyone is going to have it lying around, I just happen to have a 1885 Winchester Low Wall that uses them. Other cartridges I had just didn't work out, either too big or small. Cut the primer pocket end off with a pipe cutter and solder it onto the funnel.
It does work very well, at least when using a stand (does require two hands). I load the powder in all the chambers first. The left hand holds the flask, right hand the measuring gauge, press the button, a few shakes, stick the funnel in the chamber, tip over, rotate the cylinder, and your ready for the next chamber. It loads fast without the worry of trying to line up to avoid spilling any powder. Works well if your making paper cartridges also.