If you don't have any luck with the Facebook group, I met a fella down in Southern PA last fall who has a garage full of Capri parts (and a Capri). I'm like 80% sure he had a spare front bumper, and I'm like 90% sure I still have his phone number. If you are anywhere nearby to the Reading, PA area, I can find out if he's willing to sell it. It wouldn't make financial sense to ship one any great distance, they are rather large and heavy.
As far as fitting a different bumper, that's gonna be a challenge. Unlike modern cars where the front bumper cover is just a thin plastic shell held on with nothing but clips holding it in, the Capri front bumper is the old-school steel front clip type of deal. The whole front end is essentially the bumper, including the crash structure. So to swap it with another car, you'd need to find something that's both old enough to be setup the same way, and with a skinny enough wheel base that it wouldn't look silly. Ummm, perhaps something like a 240z bumper, or maybe even something like an early 90s Dodge Dakota bumper? A super old Subie maybe? Good luck with that one