Night Vision Vortex flip cap for UTC-Xii :

[deersniper]

Vortex Defender Flip Cap Objective Lens 56 62-66mm O-56 875874005907 | eBay

DEFENDER™ CAP OBJECTIVE 56. New for 2016. This is the last flip cap you will ever need! Virtually indestructible, this cap will fit snugly on nearly all Vortex Optics® and features a snap flat spring that will keep your line of sight unobstructed.

www.ebay.com

Credit to @TheHorta

 

[TheHorta]

Very snug fit. No modifications necessary. 95% perfect. Locks up tight.

Also, using the same cap on a Halo-LR as well.