I think you have to talk to your own PD. You are going to have to at some point, best to do it as early as possible so that contingencies can be worked out. You don't want to sneak around, looking for a new program, and then when everything is worked out drop the bomb on your program that you won't be around the next year. That doesn't sit well with people. If you are transferring for a good reason everyone will understand, but they will be less understanding if you skip out at sudden notice.
Plus, the PD will be familiar with the procedure, and likely in contact with others and will know the situation around the country, and probably where there are openings.
I don't know the answer to your question about where positions are posted.