PCIE ssd upgrade for 2015 Macbook pro or use WI...

Just purchased a MID-2015 15.4 Retina MBP. The machine comes with 256 PCI SSD. I would like to upgrade to 512gb, is there anything on Amazon that is compatible? i.e, Samsung or WD?

256gb is probably OK for now. My other thought is to use an external wifi drive for data only. I tend to store a lot of Music more than anything else.

Thanks!