These are some elastic threading needles I came up with to allow my wife to more easily thread elastic(obviously) when dressmaking.

print the needle you want, the hole can be a little smaller than the elastic, feed the elastic as in the picture or whatever works for you. (I used some yarn as I had no elastic to hand)

If you can't see the size you need, then simply scale up or down sideways, not Z.

Sometimes it shows how handy it is having 3d printer in the first place.