Does Apple sell a 1TB of internal PCIe-based flash storage to replace the 250MB that I have in my Mac Pro?
Mac Pro, OS X El Capitan (10.11.6), has 250MB storage need 1TB storage
There's no compelling reason to buy stuff like that from Apple. Are you definitely talking about a Mac Pro? Is it the 2013 model, with a 256GB (not MB) flash drive? If so, replacement is very expensive.
I've been looking for one myself, but not bought it yet. But I think the best is to just type "ssd 1 tb Mac Pro late 2013" to the search in eBay.com. You'll find the cheapest original ssd PCIe drives.
Firstly which model computer do you have? Is it the old classic Mac Pro silver desktop? Or the new(er) Black round Mac Pro desktop, or like a lot of people do you actually mean a MacBook Pro laptop?
If you have the black round Mac Pro desktop aka MacPro6,1 aka MacPro 2013 then this uses a single internal Apple SSD drive which is a PCIe style SSD using a proprietary Apple connector. Apple do not sell these SSDs as separate items unless possibly you are an Apple authorised repair agent and can buy it as a spare part. However these Apple drives are often on sale on eBay as mentioned by Malarian. The ones on eBay have either been removed from another Mac, or possibly 'liberated' from the Chinese factory.
Note: Apple have produced two generations of their SSD drive, the SSUAX and the SSUBX. The SSUBX is nearly twice as fast as the SSUAX.
Note: The original Mac Pro 2013 SSD will have also come with a heatsink attached to it, the version of the SSD used in MacBook Pro laptops and iMacs does not have this heatsink. Whilst the version without a heatsink will work in the Mac Pro it is possible that under heavy usage it might overheat.
As indicated by kahjot it is now possible to buy a brand new third-party SSD drive for the Mac Pro 2013, this obviously will not be a genuine Apple part but will work fine and have a warranty.
Should you have one of the older 'classic' Mac Pro desktops it is possible to get a PCIe adapter card and fit an SSD to it including the above mentioned proprietary Apple versions. I have done this myself with a SSUBX model 1TB SSD.
Call the Apple Store and ask. Or you can shop for one at OWC where you can also get a sled adapter for use with a 2.5" SATA drive in a Mac Pro.
Does Apple sell a 1TB PCIe flash drive
