Second Lion system disk

I am buying Final Cut Pro X and best practices calls for its installation to be performed on a drive/partition separate from the current startup disk if one currently has Final Cut Studio (2009) installed there--which I do. This separate drive/partition will, of course, have to have a version of Lion installed on it as well. However, having just found this out, I was not in any position to create an install disc when I purchased Lion, and since it was download only I don't see how I can do this now. Do I have to make a separate purchase of Lion in order to install another version on a separate drive/partition?

And yes I know I can install FCPX on the same disk as FCPStudio provided I jump thru the right hoops, but I would prefer to keep them installed separately.

thanks in advance