If you have an air-cooled CPU, the top fan is not there, if you have a water-cooled one, it should be there.

It is interesting that they started including the VRM heatsinks with the air cooled model . . . at least in the promo photo.

@ProfessorW00d​ 

This shows the real face of DELL

1. Side light (optional)
2. Top-chassis fan (optional)
3. 3.5-inch hard drive
4. Front-chassis fan (optional)
5. Memory module
6. PCIe fan
7. Graphics-card end holder (optional)
8. 2.5-inch hard drive
9. Coin-cell battery
10. Graphics card
11. Power-supply unit
12. Graphics-card bracket (optional)
13. Graphics-card bracket holder (optional)
14. Power-supply unit bracket
15. Processor cooler of the processor liquid-cooling assembly
16. Radiator and fan assembly

#2 is indeed optional.

Top chassis fan and front chassis fan may use the same fan model and proprietary fan bracket.

https://www.ebay.com/itm/165911743323?

https://www.amazon.com/Deal4GO-Chassis-Replacement-Precision-Alienware/dp/B0C7CYDDQZ

also used in XPS8950 etc.  and remarked on as example of Dell hardware overengineering in oem case instead of standard 120 mm fan mount mechanism 

@redxps630​

On Aliexpress, a new original fan for Alienware for 10 euros