The Classic Helmet Pack rotates into the in-game store every so often. We never know when it will be though, so hold on to at least 150,000 points so you can buy the pack when it comes around.Oh, good to know! Thanks!
Do you know if is it anywhere advertised when it rotates in? I see news about game modes rotation in Twitter and Instagram and so on, but haven't seen about REQs rotation.
As others have stated, 343 never announces when the packs are coming back so they are always a limited time surprise. They can come and go quick sometimes so if you miss it, then there's your chance for a good while.
If it helps at all the classic pack was the last pack I needed as well, and IIRC I was able to finally nab it when it rotated in a couple months back (6-9 weeks ago probably). They were up for a least a few days but gone in less than 10, so like I said you gotta be quick. Not sure when the next time it will pop back up is, but I am fairly confident that we are at most getting one more chance before infinite so just keep your eyes out.
Hopefully as a final hoorah 343 gets rid of the rotational feature of the packs and just brings all of them to the regular req store, as it honestly should have always been in my opinion, as anything else is just creating a divide in the experience between those willing to pay cash and not.