I believe that the Carrier filters are proprietary and a bit pricey.

Their filter housings MAY be an option. If you're not tied into it, I would opt for a 4" filter such as an Aprilaire or other. The replacements are available from numerous sources and there are generic equivalents, if you are so inclined.

V

I bent the tabs in on my filter holder so it would hold a 4" filter instead of just a 1". I think it gives a bunch more surface area of filter media which should help lower the static pressure. I could hear it build suction as I slid the new 1" filters in place when new and it was horrible after a month and no one here smokes and we don't burn candles. I slid the 4" filter in and could barely hear any change in the air noise. I still do not see waiting a year to change it like the wrap said, that is nuts. I think 4 months is a good interval and go from there.
If you can make a 4" filter fit I would sure do it, especially if the filter media is pleated.