My second floor furnace is located in the attic and to change the filter, it requires that I crawl to the furnace and lay on my side to remove the furnace door, etc. I'm looking for air returns with replaceable filters to install in place of the 8"x16" returns in the three second floor bedrooms. I would be willing to use a larger size return if needed. I'm hoping this would eliminate the need to have a filter in the attic furnace. Does anyone have a source for this type of return and the replacement filters? Thanks.