And this is why we are lucky that there are so many caging manufactures, someone out there will meet your needs at some point.
I can only suggest asking someone who has them to possibly ship them to you, or if you know you're traveling (i usually travel to several different states depending on what im doing for various things) stop in and look.
Personally, one of the first things I do when considering getting a new rack is making sure i can find replacement tubs by GOING TO THE STORE MYSELF and checking for them. Usually I can't find rubbermaid tubs.
Have you tried emailing AP and letting them know you're having a hard time? I've emailed them for all sorts of strange things and they're always giving me good, quick responses usually within a day.