1.) Chapstick Marker:
-you can use pretty much anything that will solidify to seal off the bottom of the chapstick. The easiest is candle wax, but it cracks / comes loose from the bottom of the container very easily. You can use plain white-glue too, that seems to work for me. In any case, put a strip of electrical or duct tape around the little rotating bit on the bottom of the chapstick to stop it from turning. More often that not, that's what causes them to leak - that little bit will get rubbed and turn, causing the wax or glue on the inside to break away from the base, and leak all over your pocket.
2.) Eraser Nibs:
- Same thing happened to me a few times. I ended up racking a few tubes of super-glue / crazy-glue, and it seemed to solve my problems. Just put a bit of glue around the inside of the opening to the mop, then fold the strip of eraser as usual and stick it in.. give it some time to dry though before you use it. Only problem is, once you do this, good luck refilling that mop ever again. I use bingo-dabbers and cheap shit like that to make my mops, so it's no problem to toss em out and go get more. If you're using a mop that you want to reuse later, condiser finding some other material for the nib.