I bought mine directly from the BMW dealer. They fit perfectly and they have the metal X3 logo embedded in them, so they look great and match the X3 styling in the rest of the car. They stay put and don't slide around (unlike the BMW floor mats in my Z4 that constantly need to be repositioned).

I can't remember what I paid for them, but they're also sold on Amazon if you want to compare prices with the dealer.

https://www.amazon.com/BMW-51-47-2-450-512-Floor-Mat-All-Weather/dp/B0783SMYYP/ref=asc_df_B077MNQJ8Y/?tag=&linkCode=df0&hvadid=309941869364&hvpos=&hvnetw=g&hvrand=700401147194809241&hvpone=&hvptwo=&hvqmt=&hvdev=c&hvdvcmdl=&hvlocint=&hvlocphy=9030952&hvtargid=pla-569304384691&ref=&adgrpid=62060060539&th=1

(sorry, but I forgot how to shorten a link in Reddit)