The way I see it, even simply putting a small heater such as:
( https://www.amazon.com/gp/product/B0C3VS2T9Q/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1 )
from amazon into a clear sterilite box would get you halfway toward having your own DIY filament drier. To avoid hot spots that might damage your filament, pick a bigger box, and perhaps put in some extra fans inside the box to further even out the heat (similar to a convection oven).