where can you download os x lion?

As of right now, Lion is still available if you call the online Apple Store. They will ask for your Apple ID and credit card number and will then send you a code which you can redeem in the Mac App Store. Cost is the same as it was; $29.99 plus applicable tax in the US

Alternatively, you may still be able to find the USB installer at a local Apple Store or an Apple dealer, though available stocks will probably disappear quickly if they have not already. Otherwise you'll have to look for the USB installer on the open market, such as through eBay or a Mac User Group.Those are probably starting to rise in price

Regards.

Forum Tip: Since you're new here, you've probably not discovered the Search feature available on every Communities page, but next time, it might save you time (and everyone else from having to answer the same question multiple times) if you search a couple of ways for a topic, both in the relevant forums and in the Apple Knowledge Base, before you post a question.

You can't.

I afraid you are too late - Apple pulled Lion from the App Store when they released Mountain Lion.

You could try contacting Apple to see if they could give it to you on a flash drive or DVD, but I'm not sure they can.

Or better yet - don't listen to me 😝

varjak paw has given you a better answer 😉