The mono to stereo adapter from Amazon works well! It’s a pretty small adapter, that converts a mono encoded MP3 file (such as an audiobook coded mono) instead of just playing in one ear (left earbud) it plays in BOTH ears (same channel). So this is just the way it should play mono files, until Sandisk fixes this (Not gonna happen). It’s $3.74 and if you have Prime, you can get it in 2 days.
It is very light and appears to be well built, except of course that it sticks out a bit. It’s really not too bad, considering you don’t have to recode all your m4a files!
This is the link on Amazon if you want to order. Also pic attached of what it looks like on the SanDisk Clip Sport:
https://www.amazon.com/gp/product/B0002EOHX0/ref=ppx_yo_dt_b_asin_title_o00__o00_s00?ie=UTF8&psc=1
