This is the DryDock spool holder, 'cuz you know, it kinda looks like a boat.  It's a dry box that uses a 1 gallon Ziploc bag (now with more options) to enclose the spool, has space underneath for desiccant, and an opening for tubing commonly used in Bowden configurations.  It is also my entry for the 3D Printing Nerd spool holder build challenge so it is designed to fit on his shelving but will also sit on flat surfaces.  Most common filament types should work fine for this print.  It was tested using 65mm wide spools but the boom has room for up to 80mm wide spools, however, depending on how tall they are the bag may not allow them to spin freely.  BTW, I realize my attempt to use easily found materials for myself probably made this US-centric.  I don't even know if Ziploc is an international brand so if anyone outside the US would like to figure out the scaling for your locality that would be awesome.  I can upload a template if anyone is interested.  Smaller is probably not an option for most spools unless they are just making the bag shorter rather than making it narrower.

Edit:  It was kind of bugging me that in my effort to make a drybox with an enclosure made from materials I had easy access to I may have limited the design to only people in the United States so I decided to add some options so that the DryDock might be useful to more people.  I have added files for a bow+ and stern+ that do not have the protruding seal around the perimeter.  This should allow for a much wider range of options for the enclosure.  Now any bag that will fit around the spool holder and spool can be used and fixed with a rubber band or better yet wide rubber bands under and over the bag for a really nice seal.  Experimenting, I was able to epoxy just the ziplock portion of a bag (inside-out) to the PETG which could theoretically allow for an actual Ziploc seal.  I also added a 22mm boom+ with 608 sized bearings and a mast+ to accommodate the slightly larger diameter boom.  The original mast is designed for a 20mm diameter boom and will still function with the boom+ if you have already printed it.  Finally, I drew up a little cap to fit 4mm PTFE tubing if you might want to prevent air from making its way up the filament port while the spool holder is not in use.  I hope that these options might make the DryDock useful to a larger amount of people as well as possibly extending the life of your desiccant.  I added pictures of the boom+ and cap (yes printed from the DryDock).  I have not yet printed the mast+ or bow and stern+ but they are really just the same as the original files with minor tweaks so there shouldn't be any issues.