Awhile back, here in the US, someone made a one piece alloy fullel that threaded into the filler hole. I think an adapter that threads in and onto the neck of a liter of oil would be cool.
I just roll up a piece of ordinary A4 printer paper in to a cone. Tape the cone if you want but a sheet will work for one oil change. Very simple and easy with rarely any spillage.
ATF containers usually come with the right sized filler for the hole and are even simpler.
I just use a paper cone throwaway water cup that you get off a water jug at work and snip the end of it off then throw it away when im done. easy clean up. helps to disconnect the gas line off the carb too.
I use a 1ltr gear oil bottle as it has a nice pull out spout that fits nicely into the gas gas filler , just fill it up with engine oil or at fluid and away you go
I use the same thing. I've had it since I owned my 2001. I rest it between my bark buster and handle bar, fill it up and go have a beer while it does it's thing.