Stuck at the "Bunker Upgrade" part of the Raising Our Defenses quest for Season of the Worthy

I don't own the Season Pass, to preface this. I'm stuck at a quest step where it's asking me to purchase an upgrade, yet it seems that none of the upgrades on the screen are purchasable, and certainly not for those with a season pass.

So it seems the information is hidden away and poorly designed -- it turns out there's a very specific component that needs to be purchased for this step.

Right click on the EDZ Bunker Upgrades icon

Purchase the "Valkyrie Spawner: Tier 1" upgrade here.

This is the only upgrade in the list that doesn't require the Season Pass, and every other item shown requires it.