EDIT - let me know if you have any issues with these. I printed a set of the newest models recently in PETG, but I feel like a PLA with more dense infill worked better. The model fit my parts exactly how I was expecting though, so that's a plus. Also, I've added a belt block that you should be able to add to the back of your x-carriage to put the belt in the right place. you'll still need another method of tensioning the belt though.

Previous versions of this required a good bit of support to keep the motor mount hole in shape, but I printed a set of these in black PETG and they came out fine with no support, so you may be able to get away with none.
END EDIT

I made these x-ends to replace the metal ones on my Monoprice Maker Select v2 because the stock x-ends don't allow for replacing the z-axis bearings and I wanted to mess around with onShape to see what I could come up with.

As you can see in the picture I printed off a few prototypes before I came up with something that I was happy with. I printed the final revisions in orange PLA with 55% infill and 4 outer layers for extra stability, but you may want to experiment with ABS and/or a different infill % if you're going to try these. I added a space under the top of the part so the brass nut can be slid into that spot and screwed down from the top.

Also the screws that hold the bearing rods in place are m3 instead of the miniature grub screws that came on the original because I stripped out one or two of the grub screws on my machine and I have a plethora of m3 screws laying around. you just need to slide an m3 nut into the slot and screw in the m3 screw from the back to hold the rod in place.

I didn't add screw holes for the cable chain that came on my machine, but you should be able to drill a couple of holes in the back of the idler end to hold yours in place. Or you're welcome to remix these if you want to add some to the print.

Also, a couple of notes: from the original design I changed the Motor end above the brass nut to extend a little more so that the X-end stop hits at the right time, and I moved the bearing rods, motor and pulleys down and closer to the front to match what was stock on the machine so it hits the Z stop at the right time. Everything isn't exactly the same as stock, but it's plastic, not sheet metal.