Seems odd if black is -5V. That means it needs a 10 volt supply. So supplying it +5V and ground (true 0) will either ruin the module or it just won't function. The LCD module isn't going to be drawing a lot of current so you should be able to get away using something like a header connector, or something thinner, like a trimmed needle/reem, to squeeze into the top of the 20 pin connector on the right voltage without hurting wiring, a needle/ream used to just wedge into the top of the connector a little for good physical contact should work fine and not disrupt anything, trim or shrinkwrap any extra wire/reap sticking out and make sure it's seated solidly and you should be fine. This is one thing Dremel tools are great for, mount a standard male .1" square header peg as if it were a bit and then use a grinding stone as if it were a micro lathe to give you a fine point, and then dull the point just a little so you don't kill anyone =)