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They might only sell by channels (partners, like normally enterprise stuff does) - contacting them directly might let you know a possible partner with would re-sell through. I haven't looked hard enough yet because I want to ask a colleague that is from china once I get back to work. If he does not find me something quick, then I will try to contact them directly to check.

But you might find some 5/6 series like these around, just to have an idea of prices... but I think this is without warranty and/or support. And the risk is quite high... at least from my view.

https://www.ebay.com/itm/196120561227?hash=item2da9b2464b:g:8-gAAOSwWE5lcYIS&amdata=enc%3AAQAIAAAAwMzU6Ga%2FX9yYYw5bFeUcNdMoysuuCTD4F0PiagQSz9DyNhjz4rukaxG012bTu4GhSBbzsRCu%2FKL7v1hEIrVw%2FMz6v4MSkgqV83Ax6nsKZzAxcjrwTKDJeK7IYxf6qgtRus3xTlikUXf6JxXV0RMpHqTrE4fBLHeyqsS%2B%2FU61dBRGoRuWPgPtVb6aeA2GcGoK9r2%2BFaSex9wh3o3JudB2pkO6LPa7O9iva2fu%2FKEGWGDUy0hDM%2F8iHaJ%2FRkzxC%2F7YlQ%3D%3D%7Ctkp%3ABk9SR_CUz9-XYw

LMK if you get any useful info from either your coworker or from the company!

probably can use an adapter on a PCIE slot

Yep, should be possible for NVMe (only) devices behind U.2... SAS or SATA you will need a controller. The beauty of NVMe is this simplicity.