UITableViewCell *cell = [tableView cellForRowAtIndexPath:indexPath];
CGRect accessoryRect = cell.accessoryView.frame;

int detailDisclosureSize = 24;
RectangleF accessoryPosition = new RectangleF(cellPosition.X + cellPosition.Width - detailDisclosureSize * 2.45f, cellPosition.Y + cellPosition.Height/2 - detailDisclosureSize/2, detailDisclosureSize, detailDisclosureSize);