Hi @harrypearce
The palm rest assembly can be replaced, however you have to completely disassemble the laptop to do it.
Here's the [https://dl.dell.com/manuals/all-products/esuprt_laptop/esuprt_xps_laptop/xps-13-l321x_owner%27s%20manual_en-us.pdf|owner manual] for the laptop. Go to p.63→ to view the procedure to remove/replace the palm rest assembly.
Search online for [https://www.google.com/search?q=Dell+XPS+13+L321X+palm+rest+assembly&client=firefox-b-d&sca_esv=578828967&ei=d7NDZfwZ6eGx4w-kyL94&ved=0ahUKEwi8sarJxKWCAxXpcGwGHSTkDw8Q4dUDCA8&oq=Dell+XPS+13+L321X+palm+rest+assembly&gs_lp=Egxnd3Mtd2l6LXNlcnAiJERlbGwgWFBTIDEzIEwzMjFYIHBhbG0gcmVzdCBhc3NlbWJseTIFEAAYogQyBRAAGKIEMgUQABiiBDIFEAAYogRI1hRQgQdYgQdwAXgAkAEAmAGiAqABogKqAQMyLTG4AQzIAQD4AQHCAggQABiiBBiwA-IDBBgBIEHiAwUSATEgQIgGAZAGBA&sclient=gws-wiz-serp|Dell XPS 13 L321X palm rest assembly] (supplier examples only) to find suppliers that suit you best.