Sounds like you are referring to the OEM clear plastic covers that Subaru sells in other countries but not in the US.
I had both at one time, got them when the car was still new. The headlight covers had to go when I changed to Morettes, but the fog covers stayed on until just recently. They did their job well and the only "issue" was a small crack at the bottom of one of the headlight covers that did not affect its function or the light output.
I would still have the foglight covers except that one of the fogs got broken by a direct impact that took out the cover as well (nothing would have prevented the breakage in this case). Since replacement covers are not readily available I got some Xpel and now the fogs are protected with that. I have Xpel on the Morettes also and it has been very effective. You may want to consider this as an alternative.

 

The OEM covers (sold in Australia, UK, maybe Canada) are hard clear plastic and clip on over the lights. On the headlights there is a small metal clip that goes on the top of the headlight with adhesive tape, a hole in the top of the cover fits this tab and then it clips over the bottom of the light. On the fogs they just clip on with no added hardware.
Xpel, or Stongard (similar products) are a different story. These are clear flexible acrylic material with adhesive on one side, and are applied directly to the lens or light cover. You can get them either custom pre-cut to fit your lights, or in bulk uncut sheets that you cut out yourself. The DIY method is cheaper and it's easy enough to cut out circles for round lenses like the fogs (which aren't perfectly round but close enough) or Morettes. For a complex shape like the stock headlights the precut may be the way to go.
Xpel/Stongard is permanent, although it can be removed without damaging the lens. However once removed it can't be re-used.
More info here-
www.xpel.com
www.stongard.com