I have a set of Vampire adapters like the one you are looking for, typically used to adapt a single spade into a banana. If I open them up to the largest capacity it gives you an opening of 3/16" so your 2 spades would have to be pretty thin.
Audioquest makes one that looks like it might work for you. Here is a link (I cannot speak for the seller - just found it on quick search):
http://www.thecablepro.com/spade-to-banana-adaptor-audioquest.html
Audioquest makes one that looks like it might work for you. Here is a link (I cannot speak for the seller - just found it on quick search):
http://www.thecablepro.com/spade-to-banana-adaptor-audioquest.html