Non-expanding foam is common in the US and not too hard to find. If you stick the nozzle all the way in you'll get most of it where it needs to go, it will flow back toward you as it fills. It sets up somewhat solid- not perfect but enough to keep movement to a minimum, and even thin trailer-grade pans should handle that for awhile. With the small hole on the outside of the pan, it won't see hardly any water and a dab of caulking will make it look decent.
As I said, it's a patch and not a fix. It may buy you enough time to save the money needed to do it right. I've done similar with tubs and I know it works, but not forever like a fix does. If you don't have any other alternatives it's worth the $15 it takes to try.
Phil