I have ordered these stems from eBay:
https://www.ebay.com/itm/224467814348?var=523251044300
Cheap carbon stems and used them on both my MTB and my road bike. Pretty lite and have held up to all sorts of abuse. I use a 60mm version on my 26" "huck" it MTB, a 70mm on my 29er and a 110mm version on my road bike.
Run these for over 5 years without issue. Would never spend big bucks on a stem again.