iPhone Developer Needed

We are looking for an experienced iPhone developer to take over maintenance of an existing ebook application. This need has come about since our developer has moved on to a Drupal opportunity he couldnt pass up. We have the source and the git database. The developer is available to assist with the transition. For the purposes of vworker, we would like to purchase a block of hours every month which can be billed against. (following agreements on work to be done/cost to do it)