This is a two-piece clip to hold the folded-down-edge of a coffee filter inside of a folded down tubular bandana (sometimes sold under the brand name "Buff"), so it doesn't squeeze your nose down, nor allow your breath to go back into your eyes alongside your nose.
I may have to try this with a piece of blue shop towel, if I can find any, as that may be more breathable and do better filtering than a coffee filter. For now I've only tried it with what I had on hand.
The coffee filter (or piece of blue shop towel) will add a bit more filtering than offered by the stretchy tubular bandana fabric by itself, and covers both the nose and mouth. The coffee filter (or blue shop towel) will absorb moisture from your breath eventually and should be discarded and replaced after use (you buy coffee filters by the hundreds for a couple of bucks. I'm not sure if anyone has blue shop towels still in stock as of today). The tubular bandana/Buff should be washed frequently.
The shape was inspired by other nose clips I've seen for sewing onto homemade fabric facemasks, but you can't nest those together. The shapes for these two pieces were drawn in Inkscape, then imported into TinkerCAD. The spikes and holes were added in TinkerCAD.
Assembled, it is still thin enough in PLA or PETG that it flexes somewhat, but it could be potentially be warmed in very hot water or using a blow drier and carefully custom fitted (don't burn yourself, however).
No guarantee of protection from any specific disease or type of dust or other contaminants is offered or implied. It is just an aid to help a homemade mask potentially work somewhat better, and to keep your breath out of your eyes.
It should print without supports needed as the gap between the spikes and holes is pretty small. You do need to carefully separate the pieces after printing. This may be difficult if you over-extrude. If anyone tries blue shop towel pieces and find this works, please let me know.