Hi John, I've used the clear waterslide laserjet decal paper as well, but not on drop targets as yet, should be ok with mylar over it.  

I buy the mylar from Bumper Action, in pieces large enough to do a whole playfield, after i mylar a pf there are usually offcut pieces leftover that can be used for drop targets etc. I think it was about $60 a sheet last time i bought some. If you dont want to go to that expense or have no use for a large sheet, i have heaps of offcut pieces laying around, i could send you some to use if you want   I'm moving house at the moment and its all packed away but if you can wait a few days i can find and send you enough to do your targets.. PM me your postal address if you want some to try and i'll send soon as i can  

Cheers.. Mitch