Plenty of flex cables on AliExpress. (821-00010-A SSD PCIe flex Cable for Mac Mini A1347 2014 2015) But they don't have the correct accessory parts. Many do come with screws for some other drive and logic board removal tool.
I got Transcend JetFlash 820 480GB version. Requires MacOS High Sierra 10.13. Works fine but doesn't come with screw. JetFlash 825 version is designed for laptop user who have existing proprietary Apple SSD to put into external case.
Transcend's JetDriveToolbox software has TRIM enabler.
JetFlash is preformatted with MBR. So use Disk Utility to erase and format the devise with GPT (GUID Partition Table). Carbon Copy Cloner works great for cloning. Also fixes the recorvery partition. Or can clone for free with unix tools.
BlackMagic Disk Speed Test says write up to 620MB/sec; write about 720MB/sec.