I would suggest buying a low-power PC in a mini-tower. Just enough of a machine to fit your PCI board in. Anything I have seen has cost more than such a PC.
You can even probably get it used to spend less money, but even a low-end PC will cost under $1,000.
Nothing I've searched for will connect a USB port to a SAS device.
If you really wanted to do this, you'd have to do a lot of work. I'd start by looking up the PCI bus' electrical specs so that you could connect to it. Then you'd need a power supply to power the tape drive and probably the PCI board.
Then the real work begins: you'd need to write a custom driver.
Just get the PC if there is a driver available. Otherwise you have an interesting-looking paperweight, unless you are very good at electronics and programming and have a lot of spare time. I like these things and are good at them, and I wouldn't try it using a Raspberry Pi unless somebody were willing to throw a lot of money at me.