As far as I know, SFF-8087 is a connector used for SAS exclusively. You cannot "adapt" it to PCIe because the SFF-8087 port on your motherboard literally does not go to PCIe lanes directly – it only goes to a SAS disk controller, just like the SATA ports on a PC go to a SATA controller.
(While PCIe is general-purpose and can be "adapted" to become a SAS/SATA/USB port by connecting an appropriate SAS/SATA/USB controller in the middle, the reverse is not true; an adapter cannot bypass the SAS/SATA/USB controller that's already there, unless it was specifically designed for. USB has Thunderbolt for this kind of "bypass directly to PCIe", SAS/SATA generally do not.)
This is different from e.g. SFF-8639 (U.2), which is a connector that does typically provide PCIe lanes from the beginning, just in a different shape, so of course there are adapters that just convert it from one form-factor to another (the same way as M.2 "NVMe" slots are really just PCIe slots and have adapters both ways).