I reinstalled tiger on one iMac, but want to re-upgragde it to Lion. I don't have the discs anymore, but I installed Lion from the Mac App Store. Now that I'm back to 10.4, I don't have the App Store. I have a new iMac with Mavericks, but it won't let

I have a 2006 iMac that I've upgraded to each new os as they came out. I just wiped it (for the kids to use, I have a new iMac with Mavericks) and reintalled Tiger from the original discs. I want to get it back to Lion - which I purchased from the Mac App Store. But Tiger doesn't have the App Store and I don't have the discs anymore from the intermediate versions. I tried downloading Lion from the new iMac but it's not available...

Any ideas?