Broken part in casement window, do you have in metal?

Looks like you need a new tie bar guide. I'm afraid that these aren't made in metal. The manufacturer strictly only makes these as-is. I would imagine they want to avoid metal to save on production cost.

That said, these shouldn't be breaking as often as you've suggested. They should be lasting years. There may be something else at play here. Can you describe exactly how they're breaking? Can you also tell me how many guides you use per bar, and how long the bar itself is?

Tom's right, the manufacturer does not make a metal version of this tie bar guide. I believe the reason being that they would would rather have the nylon guide wear out and not the tie bar itself, which is what would happen with a metal guide. 

Our 39-448 tie bar guide should work for you, though I don't know why yours are breaking so often. Make sure to keep the tie bar lubricated and check the rest of the window to make sure it's operating correctly. Keep an eye out for any damaged or worn hardware, or even dirt or debris that could be clogging its operation.