I don't even think a changing bag is required. While I'm lucky enough (meaning old and gray-haired) to have a small permanent darkroom, even in my youth I just loaded in a closet. I'm sure there are some who can't do this. But don't let lack of a changing bag stop you. Finding a dark place isn't that difficult.
I have a changing bag, and if I need to do something while out and about it works. But I found the hall closet is dark, and far less confining.
I load my Patersons in the wine cellar. No windows, light tight. Just ordered one of these. Thanks for the link.