We need a lot more info to give any type of meaningful recommendation. Are you wanting to replace the sights that came on the rifle, or are you wanting to add an optic? If an optic, do you want a red dot sight, or a scope with magnification? What kind of shooting will you be doing? Shooting from a bench trying to make one ragged hole, or shooting steel where a hit is a hit and speed is king?
Welcome to the forum and congrats on your new Sport II. I didn't care for my front sight nor my rear flip-up , so I replaced them for my preference and added a red-dot optic..
1. Daniel Defense A1.5 Detachable Rear Sight. Backs-up for red-dot good. $69.00
2. Front post , XS 24/7 Tactical Sight with green Tritium insert with a white outline. $63.00
3. Sig Romeo-7 Red-dot optic. $299.00
All came from Midway USA.
My advice is know what your needs are and research it out. Myself , I didn't see spending $429.00 on an eotech -512 when I could get what I got above for the same price and added to my rifle. My two pennies..
I have a tread here showing all three sights added.. (My personal..1st ar15.) . Get it the way you like and go shoot..enjoy!
Any of the steel, folding back-ups from the major, well-known brands would probably serve you well. If looking to a good, sevicable red dot, have a look at the Bushnell TRS 25. Its a 3 MOA dot that is pretty rugged and economical. I've have one on my patrol rifle for about 5 years with no issues. Paid about $80 for it.