6 Days to Chrismas. it's going to be more uncertain if you want to order anything on the internet.
So: do it yourself. You can get many nice online patterns as a PDF.
Here are some ideas for a Doctor Who / SF fan:
Knitted Dalek-inspired wristwarmers by LauraIsaac on Etsy.
David Tennant (10th Doctor) Illusion knitting pattern by Woollythoughts on Etsy.
Pattern for a toy rocket by DIY Fluffies on DaWanda.
Crossstitch pattern for a bookmark, Doctor Who "The library" quote: CharmingCraftsRu on Etsy.
For the illusion knit you probably shouldn't waste any time, if you want it ready before Christmas. It looks awesome though (maybe for a vest or sweater?).
I once knitted a "Madness" illusion scarf for my BF and did the whole project right in front of him. He never noticed. ;) You'll have to keep focused though, a few times I noticed my mistakes many rows further and had to unravel part of the scarf!
The other patterns can make a fun last minute weekend project.