Tetra Whisper Easy to Use Air Pump for Aquariums up to 10 gallons. Ships free with prime or $25+. $4.07 @ Amazon. $1 digital credit no rush shipping eligible as well.

$4.07 shipped with prime or $25+ qualifying orders and eligible for a $1 no rush shipping digital credit as well.
I believe this is the lowest price ever for this item, at least the lowest price I could find previously was $4.29 and it made front-page on SD. A steal for this air pump IMHO. Cheaper than the no name brand pumps.
https://www.amazon.com/gp/aw/d/B0…prod_image