How to fix slide hook next to button on slacks?

Hi,
The exterior hook part of the slide is missing, the other half is still inside the waistband. I removed both parts from another pair of pants hoping to "transplant" them, but now that I see the whole apparatus, it's really more like a hook that's been stapled thru the two holes on the base. I can probably pry the staple parts up, but then will need o open the waistband to insert the base? I hope this makes sense to someone out there. I'm new to sewing and this is way over my head. (And, btw, an emergency sort of. My husband needs to wear these to a golf tournament starting in a couple hours...)