Text from Shield with Command Block (Minecraft)?

A few friends and I have a survival server and you can find in dungeon and so gems (the server currency). And we want to build a system where player heads can be hollowed out. With the Redstone and so I know myself quite well so that's no problem. My problem is Command Blocks. So my idea would be to throw in the money, write the player name on a sign presses a button and you get the head matching the sign. You could probably do it. Also make a renamed item with player name to throw or something.

What I'm looking for would be that someone probably. The commands for the command blocks are sent. I need a command to copy the name of the shield into a variable and then a second one to give a player's head that belongs to the player from the variable.

I can make a complete money system with command blocks. But as far as I know, you have to code for what you have before a plugin. If you want to have that with the money system write moch. Btw, with the money system you could make your idea. Lg