I have an excellent condition MAD back up iron sight for sale, in excellent condition. Very minimal finish wear on the contact points where it flips up, never fielded or abused.
This is the older style, non-locking variant. Up to you to decide if that's an asset or not, I've honestly never had an issue with it flipping down at a bad time, but it has flipped down once or twice and saved me from getting snagged on a sling.
Can I hear $80 shipped US?