I downloaded and printed emacs bike lever and was impressed by the sturdiness of the design and how nicely the prying end was crafted. But his design got wider at the end and the split tail for hooking to a spoke seemed to require printing supports. So I modified his lever in two ways:

1) I made the lever the same width over its entire length. This reduces material used and does not hurt strength on the working/prying end.
2) I got rid of the split tail and changed that end to have a larger single spoke hook so that no support is required when printing. The tip of the hook also works nicely to depress the valve core in Schrader valve equipped inner tubes.
3) I made a simple sleeve so that you could store three levers together in a compact bundle. You only need two for tire removal, but having a spare is a good idea.

These levers are sturdy and have survived removing and re-mounting a fairly tight 27" road tire multiple times. I printed this with PETG which has a slick surface that I like since it slides against the tire rim. PETG will break from impact, but is tough under non-impact loads.

Print the levers on their side and use 4 or five walls. I printed with a 0.5mm nozzle specifying 0.6mm lines and a 0.24 layer height. Infill was 60% Gyroid in Cura. You should print so that the curved prying end is solid with no infill. I provided the Cura as an example of that.

I printed the sleeve/holder at 100.5% of its standard size. You may find that you want to make the holder a slightly different size in order to get a nice tight friction fit.

As they are, these levers seem a bit large for carrying on the bicycle. I may make a narrower set and see if they hold up to the strain of removing my fairly tight tires.

Note: I've been using these levers a lot in a bike shop that fixes up old bikes and gives them to kids who need bikes. These are holding up quite well. That said, they are not indestructible. It is possible to break the tip off with very tight fitting tires. But you'll probably know when you are in that zone since you'll be putting a LOT of force on the lever. Keep these in a set of 3 so that you'll have two in the rare case where you might break one.

All breaks are across the layers so far so are simply a limit of the PETG plastic I'm using and the cross section of the lever. If I make the lever thicker in that area, the levers become less useful since it is important to have a thin profile where you insert the tool under the tire. If you have access to a stronger or tougher filament, then that should be more durable.

Update 7/12/2022 .................
I've uploaded a modified v5b file that makes the end hook a bit more robust. I've broken a few hooks off - mostly by dropping the lever. I've been using these a LOT while volunteering for a group that fixes up donated bikes and gives them to kids that otherwise wouldn't have a bike. So my levers are getting a lot of use and are holding up very well. It is possible to break them on a very tough tire, but overall they seem about as tough as any of the other plastic tire levers in the shop.