I just keep my gallon in the shower but I know it's bulky and doesn't work for everyone. I also keep all my caps that come with my bottles so when I can no longer pump I put the cap back on and turn them upside down. When I have a bottle that is upside down I open a new one and use it until there is room enough for the rest of the old bottle. Then I use a funnel and prop up the bottles so the old one can drain into the new bottle. I don't do this with the gallon but my other size bottles it works great with. I imagine the gallon would be more difficult to have on the top but you may be able to prop them up somewhere so they don't tumble. I like using the gallon because it's just 1 pump for me. I get some 16oz and some 32oz auto delivery and when they come, in the same formula as my gallon I just transfer them to the gallon. My other formulas I just use the funnel way. Sorry, don't think this is to helpful but maybe try the funnel. Or if your husband is like mine, he'll wanna MacGyver something for you! Lol!
Love my Wen, Love my Animals! God Bless You All!