Pella casement

Thanks for writing in. This looks like the attachment at the end of the 39-386 Egress Pella Operator (its opposite-handed counterpart is the 39-385). Unfortunately, these parts are not sold separately from the operators themselves, so you'd have to replace the entire mechanism. I apologize for this inconvenience. Just make sure the operator specifications matches what you have before proceeding. For a new handle, see the 39-109B. 

Alternate image for 39-386

As far as the hinge arm, Pella makes a few different kinds depending on the size of the window. See the 39-351 & 39-352 9-5/8" arms, the 39-39-394 & 39-395 10" arms, or the 39-396 & 39-397 12-1/8" sets. See if one of these matches what you're looking for.