Getting Irix or sub OS for used SGI boxes...

Hi all I recently started to find some SGi boxes up here. Some old (Personnal Iris 4D/20, Indigos) some not too old (Origin 200!) These could be considered a bit rarer up here in Canada. All with blank HDs of course... But now I run into the problem of finding an OS for these....since Irix is expensive and/or hard to find... Ports of NetbsdMips or Linux for Mips seem incomplete, very experimental and only support a few boxes... I wonder if that what a wise decision of SGI to keep even old obsolete versions of Irix "closely guarded" like they have... I compare with Sun Solaris and the Sun decision to make it free...doesnt that make so much sense?...when we see SGI and Sun are struggling in a PC/Windows dominated market? I also think about SGIs decision of using all the proprietary simms and dimms in almost all of their machines, how wise was that? Anyone that can help me with my hunt for a cheap and recent to semi-recent version of Irix, please contact me. Thanks Claude