I note from the first post that this is a 1.4 engine and not the 1.7. I think the 1.4 may possibly have had a plastic rocker valve cover, looks like it in the Haynes Photos, but I maybe wrong, as I have never worked on the 1.4.
If you have a metal cover , as Red said they are usually ok. The problem is the rubber from the heat goes very hard and stops sealing properly. Sometimes you get a way for a short while with no leaks but the problem will return within a few months unless you replace the gasket.
Elring are good, OE quality, however with a 1.7 engine the price of the gasket didn't appear to include the 4 rubber fixing grommets and cup washers where it bolts down.
The gasket I bought for the 1.7 was made by AJUSA in Spain and although I had never heard of them before are apparently OE quality.
eg for the 1.4 check your engine code matches FHF FHD , I note this states the rocker cover is Aluminium not plastic as ?I thought. I would have thought that the Puma 1.4 was the same as the Fiesta 1.4 Zetec. So search for that also using your engine code.
https://www.ebay.co.uk/itm/Valve-Rocker-Cover-Gasket-FOR-FORD-PUMA-1-4-97-00-CHOICE2-2-Petrol-EC-Elring/372458912076?fits=Model%3APuma&epid=12024460703&hash=item56b847f94c:g:SfwAAOSwnFpbtlHZ
On the 1.7 , it fitted better than the FAI (that was hopeless) it still required RTV silicon to hold it in the cover before fitting.
I always use Granville black RTV off ebay , it's approx £6.50 for a 300ml tube that fits in your sealant gun.