No need to produce them when cosmic rays are everywhere already - if one wants extra exposure, book lots of airline flights, especially those travelling near the poles, with as many connections as possible to maximize flight time; earn more frequent flyer miles.

Computers (and devices containing them) are increasingly effected by cosmic rays as they get faster / circuits get smaller and smaller - fortunately, the effects (often random bit flips) are nearly always transparant to the user who never notices anything amiss; most folks are used to their computer locking up / misbehaving once in awhile for seemingly mysterious reasons already.

On a related topic, there many studies / experiences that suggest very limited exposure to various toxins, including radiation (I think that's the idea you may be getting at in regards to cosmic rays), etc may actually be healthy; "hormesis" - google for more information.

Ron