Try this web site for replacement keys. It may offer some help but worth a try. [NAME] may be right that your only alternative is a palmrest assembly.
Hello,Today my alt keycap just broke. I was unable to find dell replacement parts online. I am a designer and I use the alt key a lot. I don't want or have money to replace the full keyboard. If any of you had a similar problem please share your solutions.    [IMAGE]
Where to buy alt key XPS 9310