You've been able to get the little twin packs from Morrisons for ages - a couple of years at least. I found them very handy in my first few months doing SW...we're 50 miles from a Morrisons, and anytime we're passing, hubby goes in to get pies & sausage rolls, cos he says they're fab (?! lol), so I would grab some fresh fruit and a pack or two of HB eggs to eat in the car! lol I wouldn't use the salad bars though - they always seem really unhygenic to me?
Much, much more recently we came across the Happy Egg ones in Asda. I think they move them around though, cos I've only seen them a couple of times, and I'm SURE they are never where they were before, IYKWIM.
I've never spotted them in Tesco, but I haven't ever looked there, either.
Flutterby - eggs never last in my fridge for more than a day or two, and I cook off 10/12 at a time! lol