newegg offers the 10mm-thin HP Elite L2201x 21.5" 1080p LED-Backlit LCD Monitor, model no. LM917A8#ABA, for $79.99. Coupon code "DSKBNCE23" drops it to $71.99. With free shipping, that's the lowest total price we could find by $17, although it was $2 less a month ago. It features a 1920x1080 (1080p) native resolution, LED backlight, 5,000:1 contrast ratio, 250 cd/m² brightness, 16ms response time, and more.

Of note, this has a DisplayPort only, so you'll need an "active" adapter for other connections.