No you're not the only one that's had to replace those filters. Check out this thread

After some time I did manage to get new filters from someone in England. Until now I haven't tried to put them in, but I just did and one seems to fit okay. It is loose and free to move but I don't see how it would fall out. You might to double check the size of the filter it should be 15x30mm. If I get a chance tomorrow I might give it try and put mine back together to see if anything shows up.