I know Matterhackers recently stopped selling master spool filament from Keene Village Plastics because they were not selling. I would like for you to reconsider. From my experience purchasing them from you I believe the primary reason they were not selling was because few people knew that Matterhackers did in fact sell them. Although they were posted on the web site, the master spools were not listed in your normal list of available filament. I needed to specifically ask if you sold a master spool option and I was told I needed to do a search for the spools. Once I knew how to get them I did so every chance I could.
Since it is very possible the lack of sales of KVP master spools was because of lack of knowledge, I would propose that you try to sell the master spools again from KVP (or any other supplier really). However, this time you actively promote them by making them readily visible in your list of available filament, maybe even place them at the top for a time. In addition, I would encourage you to increase visibility of these master spools by publishing a Matterhackers Minute or other article on these filaments to make sure your customers know you have them available.
If for some reason you simply can't or won't sell master spool filament from other suppliers, please get with your filament suppliers and encourage them to make their spools with a fraction of the polymer they are currently using, to offer a master spool option of their own, or to start making their spools out of a bio-degradable polymer. All three would be fantastic! Although I don't know the specifics of spool production, I would guess something with the density of a bicycle wheel, rather than the automotive wheel many spools are currently, would be more than sufficient to contain and dispense filament.
Although I love the ability to 3D print just about any object to fill a host of solutions, I am concerned about generating an enormous amount of non-recyclable plastic waste in the process. I applaud you for selling the master spool option once before and I hope you will do so again. Thank you.