Amazon offers Prime members the Kreg Standard Swing Stop for Miter Saw Fence, model no. KMS7801, for $10.78 with free shipping. (Non-members can spend $35 or more to qualify for free shipping; otherwise, shipping costs $5.59.) That's the lowest total price we could find by $18. It's designed to flip out of the way when work pieces are pressed into its face. Features include an adjustable lens cursor.

Note that it will be in stock on December 27.