They're called backup iron sights on Amazon: http://www.amazon.com/Front-Degree-Rapid-Transition-Backup/dp/B006X9DLQM/ref=sr_1_1?ie=UTF8&qid=1392869216&sr=8-1&keywords=canted+iron+sights

There are a lot of those cheap Chinese clones of the 45-degree iron sights on Amazon and they're all "backup iron sights." In fact, there's no mention of the word "canted" on that page. Though a search for "canted iron sights" turns these up as results.