Crank cover for Atrium casement window

I'm looking for replacement covers for my casement window crank handles. I was able to contact Atrium and based on the warranty number I found on the window, they said my windows are Model 871 New Construction. I have about 6 windows where the crank cover is cracked. Any chance you'd have these? Also, how do I get the handle off so I can get the cover on? Or is it able to slide over the handle? Thanks.