You might want to check the Hydro date on that bottle. If a tank fails inspection they take the valve and rebuild it for use on another bottle.
You can check on eBay for welding equipment... but. I bet you can buy or lease a full bottle for less than you'd spend on a new valve. Just one other thing. They don't fill them anymore, just exchange for a full one. So, you'd likely never see your shiny new valve again.