Some of the stuff on Amazon sold for indoor marijuana growing is probably legit, and you can easily buy cylindrical cartridges and attach an axial fan.

Or you can buy from one of the most reliable e-commerce sites in the US:

https://www.mcmaster.com/product/3722T98

https://www.mcmaster.com/product/2169K16

You’re on your own as to buying the correct size.

For what it’s worth, the IKEA carbon filters are inexpensive and appear to be legit.