REI offers its REI Igneo Regular Sleeping Bag in Castlerock for $178.93. In-cart it falls to $134.19. With free shipping, that's $165 off and the lowest total price we could find. It weighs less than 2 lbs. and is designed for 3-season use. Deal ends March 20.
Of note, it's also available in Long for $143.19 after in-cart discount, a savings of $176.