Acorn window replacement parts

I have 3 long vertical Acorn windows that crank out from the bottom. When I went to open them yesterday the top part of the window detached and had to be pushed back in from the outside. The black plastic part is cracked so there is nothing to hold the top of the window in place. Do you have the replacement part?
Please let me know ASAP as we are closing on our house today and this needs to be resolved with the buyer. Many thanks!!!
Rhona Friedman