osx lion software

Does Apple sell Lion system software anywhere in the App store. I have not been able to find it.

I am running Snow Leopard 10.6.8 on a iMac 20" Intel core 2 duo and would like to go from here to Lion 10.7.?

I do not want to go to Mountain Lion 10.8.? even though Apple tells me that my computer has the right stuff to go ahead and update to Mountain Lion.

My computer might run Mountain Lion but I think it would run slower then I want it to run. Also, I am going to get a new computer sometime this year that has Mountain Lion. However, there is nothing wrong with my computer. The problem is other software that has been upgraded to run Mountain Lion but will no longer run on Snow Leopard. Why didn't I update sooner? Because I thought they would keep Lion around for awhile after the introduction of Mountain Lion. I was wrong about that, my mistake. Can anyone give me a clue because I could use one about now.