I bought this case:
https://www.etsy.com/listing/836766161/leather-microsoft-surface-laptop-15
It fits like a glove and looks great. Has a nice protective lining along the inside to prevent the zipper from scratching the laptop. Ships from India, but with UPS Express shipping – arrived in 5 days for me.
Choose the “SurfaceLaptop 3 - 13.5” option.