Not sure if you have resolved the issue yet, but here are a few solutions:
I have a 2 week old filter for this tank that I will give you for free, as long as you can cover shipping cost. It works great and is completely quiet.
A Whisper 3i or Red Sea Deco Art Nano filter both work as replacement filters and each cost about $15. Here is my youtube review of the nano filter ([ame=http://www.youtube.com/watch?v=9hEqen4d13o]YouTube - Red Sea Deco Art Nano Filter[/ame]).
I had a problem with an Aqueon product in the past, emailed the company, and they sent me a replacement immediately. They didn't ask for a date of purchase, receipt, or even the defective product. I'm sure they would be happy to help you out.
I don't check these forums often, so if you are interested in my filter, email me (jonlong724 @ gmail dot com)