Does anyone make...

... a high-quality adapter that accepts two bi-wire spades and allows them to be plugged into a single banana jack? I've seen them for singles - Furutech makes one - but not for bi-wires. Anyone have any ideas?
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):
Audioquest makes some adapters that you may be able to use. I have some and what makes them so good is that they are very simple, but high quality. They're very small and accept a spade on one side and the other side is a banana. The only problem is that I haven't seen them in a while and forget if you can stack them. (That's when one banana goes into the speakers binding post and the other banana plugs into the back of the first banana). I got mine from The Cable Company. I would call them and see what they have. They're inventory is huge and will most likely have something that will work for you.