You don’t say what level of UNDEL2 you are working with, but this page mentions a November update. I have never used UNDEL, but have heard of others using it successfully on V5R4. It may very well be only one record at a time (I don’t know), but I’m reasonably confident you can use it more than once.
It is also my understanding (again without having used) that there are some companies that market tools with the undelete capability. ProData is one that comes to mind.