Is this what you're after?
https://www.rendcarparts.com/volvo/parts/30428668-3460983-6812818-6840228/RD18634448A
It's possible to remove the old red button with a hole in it and replace the b0rked one, but be wary of The Flying Spring. Some versions have 2 springs which want to fly and be free when the old button is removed.
ETA: Well waddyaknow - Skandix has provided a how-to guide.
https://www.skandix.de/en/documents/installation-guide/repair-button-seat-belt-buckle/3000162/