After the draft, a lot of teams will place former draft picks lingering away in their rookie league on waivers to open up room for their new draft picks. Go claim a couple of them.
Another option that I haven't seen listed yet: certainly you have to have some fodder in low-A/high-A that you can move back down to fill a role. A guy or two that's never going to move up another level and isn't seeing much time now that can be put at risk of retiring.