Sick Betta fish, won't get better

[callistra]

You're welcome. Good luck!!

[Blue Fish]

As an alternative to filters specifically made with sponges, you can usually petsmart or petco will carry large aquarium sponge sheets, it looks like a big blue spongy sheet, usually folded on itself and in a package with the filter cartridges. You can buy a package of it and then cut to fit your filter. If you ask, any clerk should be able to help you out. :)
This may be a bit cheaper for you. :)

I hope your boy is feeling better soon!

[Mirmy]

Thanks! I'm pretty sure I've seen those sheets before. My boy doesn't seem to be doing too well.. But I'm still trying my best...