i'd look at the guitar center used section on their website for a hardwire RV-7 or a tc electronic Hall of Fame.
they are right around $100 or less...both of those pedals are great for adding a little verb.
Thanks--the Digitech Digiverb sounds like the ticket.
the supernatural would probably be way overkill.
subtle isn't its strong suit, and even when trying to dial it back, i had trouble getting a nice subtle spring verb.
the rv-7, especially used, is an awesome pedal.