I just noticed this competition earlier today so I quickly put together this little keychain to go with my failed print business card holder.

Once you slide it in you shouldn't be able to get it back out. I made three versions two are just closed loops and then there is the split one that allows you to put something on before you forever lock it in place. For the spool thingy, you can secure it in place by sticking a bit of filament in as well (ideally you would hit it with the tip of the soldering iron in there.)

There are two versions of a nozzle as well one that is easy to print and another that needs some supports for sure and so does “spool” thingy.

I will add prints as I print them I can't find any decent-looking filament and any nozzle smaller than 0.6 so quality might not be the best.