Not looking to spend a fortune on onebut looking for ideas on how to bulk search haves looking for silver ones without having to unroll them.
To my knowledge you're not going to find a cheap metal detector (or possibly even an expensive one) that is going to single out silver from clad in rolls when the coins are packed that tightly together.
You'd have better luck -- that is to say, "still not much" -- by (1) weighing each roll with a good balance to look for slightly overweight ones, and (2) measuring each roll's length precisely to catch worn coins (which are more likely to be silver). I haven't been following the CRH forum lately, but as of a year or two ago, halves were pretty thoroughly searched out. I still occasionally think about doing a silver-half-in-roll detector as a "science project", but not very seriously.
Metal detectors just won't work that way, not even the most expensive detectors with all the bells and whistles.