There is no specific "open" work permit application form. You use the generic work permit form, here:http://www.cic.gc.ca/english/information/applications/extend-worker.asp
send the application in separately from the PR application and before
AIP, however you have to be very, very clear about what your request is. You need to specify that you want the open work permit application to matched up with your inland PR application, and be set aside and NOT processed until AFTER approval in principle is granted.
You should only do this if you already know your client ID number, e.g. from a previous work permit. Without that, they are going to have a hard time matching up the OWP application with the PR application.
It's probably worth writing something like "Open Work Permit Application - please match up with inland PR application and set aside until AIP" right on the front of the work permit application.
Would that work?? and that is interesting.
From everything I have read, no one has ever got an OWP at AIP, if it was not sent with the original application.
So I am very interested in hearing from anyone that did manage to achieve this. This could be some very, very good advice, if so, as many people do not realize then can send or indeed need to send the OWP at first.