I know some stuff about roof racks.....
RackAttack is a company which sells many brands of roof racks and roof rack accessories.
Since those rails have the "RackAttack" name on them, I'm assuming it's their "house brand". You know like, Duralast is Autozone's brand. And Kirkland is Costco's brand. And Top Paw is Petco's brand.
Those rack rails look very similar to Surco "Roof Rider Rails".....I wouldn't be surprised if Surco manufactured them for RackAttack and RackAttack sold them as their own "universal" roof rack.
Another thing I wouldn't be surprised of is if those rails aren't made for the xB. The reason I say this is because federal DOT safety regulations and the xB's "Naked Roof" doesn't have the necessary reinforcement for the racks fasteners to secure the rack........strap a couple kayaks on that rack and the wind resistance is gonna rip the bolts out of the roof.
In the roof rack world, the roof on first gen xB's is referred to as a "Naked Roof". Naked Roof meaning it doesn't have any factory installed provisions for a roof rack. So......roof rack companies design clamps to grab onto the top of the door jambs.
I suggest contacting Surco as well as RackAttack.......email them a pic of your roof rails and ask them to recommend "Slider Towers & Crossbar" options.
If you say these words "Slider Towers & Crossbar"........they'll know what you're talking about.
Here's a pic of a roof rack on one of my Boxes. The rack came off a Dodge Caravan. It's anchored on the Naked Roof and I reinforced under the roof where all the bolts attach. I've travelled thousands of miles and have had so many items up there: Surfboards, kayaks, bikes, cargo boxes, snowboards, etc......and nothing ever ripped the rack off the roof