The Zombie Stack Exchanges That Just Won't Die
There are some libraries that have old issues of it, as seen http://uwashington.worldcat.org/title/lego-mania-magazine/oclc/41416761&referer=brief_results.
But I'm specifically interested in a central repository of such magazines. Because if, say, I take them all out on an interlibrary loan, it will cost a lot of money.
Also, this is a general question that doesn't only apply for LEGO Mania magazine, but for all sorts of other magazines too.
InquilineKea
The Prelinger Library http://www.prelinger.com/ often has very obscure titles and ephemera that other libraries have not collected. LegoMania isn't in the collection, but a lot of other American periodicals are.