Best wishes for your Aunt, ElDee.
On the filter front, I've ordered a large piece of activated carbon filter to see how it works. It's supposed to do well for cut-to-size use. Only $8 for a 16x48 piece, free shipping. People have used it for smaller air purifiers and larger projects like replacing AC filters. If it does well with my smaller HB units, great, otherwise It's plenty large enough to use in the AC during the summer.