Bamboo toothbrushes - possibly the easiest 'plastic-free swap' to make! Bamboo handle, standard plastic bristles (the only other commercially available material for toothbrushes is boar bristle - ew!). Ergonomic handle and curved bristle shape for an easy mouth clean.
 
Buy one each for the whole family, use a crayon, marker, nail polish etc to add personalisation to tell everyone's apart.  Don't forget I have smaller & softer brushes for the kids too - they can mixed/matched for value buys, just let me know how many of each you'd like in the comments when ordering.
 
Value buys:
Any two brushes for $8.50
Any four brushes for $16