You can't buy individual keyboard parts from Dell, and it's unlikely anyone else will have them, either.  If you're in the USA, parts-people.com has only OEM keyboards and their prices are reasonable.  
Greetings, I pulled out the spacebar just to clean it off because it was sticking a bit. Now, I tried to re-attach it but it's not in the correct way. I made a video clip of it but there is not way to attach it to this message.  Are there instructions on how to attach a spacebar on this machine, or a video?   Thank you,
Trouble Attaching spacebar workstation 7750