If you want just the fan then search online for DFS2013121A0T to get results for suppliers that suit you best.
If you want the complete thermal module then try this one.
According to this supplier there are two thermal modules available.
The first is Asus part #13NR0080AP0101 and it seems to be unavailable, or at least I can't find one.
The second, linked above is for a GL503GE-1B (Asus part #13NR0082AP0301).
I don't know what the difference is but you may be able to check by comparing yours to the image in the link.
You could try searching for the Asus part numbers to see if you can find other suppliers as I didn't look too hard. ;-)
Try gently peeling off the label from the centre of the fan and see if you can see a bearing. There may or may not be a cap over it I don't know
If you can see it apply 1-2 drops only of light machine oil (sewing machine oil perhaps) to the bearing and see if this stops the noise.
Do not apply more than this as you don't want it running everywhere.
Replace the label in position when finished
Here's a video that may help as it shows how to access the fans once you have removed the cover etc. The fan label can be seen at 13 seconds into the video when the fans have been turned over.