This MAY work for you, but its going to be more bulky. Walmart, K-Mart etc are selling back to school supplies now. They have these nice little plastic boxes made for kids pens & pencils. Cost in US is usually about $2.00
You may find packaging for something or another that works. Jumbo band-aid box, womens cosmetic case, who knows? If you buy the filter, what kind of packaging does it come with right from the start? Could you reinforce taht ww/ tape or wrap a bit of bubble wrap around it?
I'm a packrat and an improvisor, love to re-purpose common things any way I can.