My dad has long wanted a version of the song 'Spirit in the Sky' by
Norman Greenbaum without the vocal track.  He only wants the music,
the original music to the song though, not by someone else.  Does
anyone know where to download something like this, or purchase a CD
with it (like karaoke music)?   I tried karaoke sites, but am hopeless
at this stuff.  Thanks in advance for any help with this question!

This might be of interest:

http://www.g4tv.com/techtvvault/features/40255/How_to_Remove_Vocals.html

iTunes has one. Dunno if it's "the" version you want, though, but it
is karaoke/instrumental.

There is at least one karaoke version of the song on "Sing Christian
Hits V. 2," but it's definitely not with the original instrumentation.
(You can listen to it for yourself on iTunes--just do a search in the
music store for "Spirit in the Sky.") So that's probably not a very
promising option.

beesocks and pinkfreud....

Pink...tried the solution given at G4 using Winamp and the Vocal
Remover Plug In...does not work well ... leaves ghost of vocals and
muddies the music ALOT.

Just thought I would pipe in and save beesocks some time.

mmmm, yeah, the iTunes version is not the one I need.  I've seen that
one before, I was hopeful because I love iTunes and know how to use
it.
I've searched karaoke cd sites, but only the lead vocal has been
removed, backup singers are still there.
Thanks canadianhelper, I was wary of that route since I'm not super
advanced when it comes to such things. (and I'm on a Mac, I think they
were for PC)
Thanks for your time so far everyone!

Beesocks...

You're welcome.  

BTW after you mentioned Apple I though 'Garage Band'(see a discussion
on a Garageband help forum:
http://forums.macrumors.com/showthread.php?t=128829) but really the
REAL problem is the MP3 format.  You are not starting with individual
tracks thus it is hard to get rid of one element.

I did come across a 'way to do it' using Audacity (which is for
linux/osx and win) and have tried it there too...same result, ghosting
of the voices and loss of audio
quality.(http://audacity.sourceforge.net/help/faq?s=editing&i=remove-vocals)

What a researcher REALLY needs to find out is WAS THERE EVER A
VOCALLESS VERSION PERFORMED BY THE ORIGINAL ARTISTS? as any 'after the
fact' manipulation seems to  be resulting in very poor results.

I'm just musing here but if someone had a copy of this on 8 track you
could likely split the vocals out no?  This is more of a question to a
researcher than to you beesocks.

For instance this site has it for $25 but perhaps if you are in a big
city a retro used music store would have it for cheaper?

http://www.thetapeplace.net/tapeplace6.html

I could probably find an 8track, I'm in Austin, TX, mecca of hippies
and musicians.  But i don't have an 8 track player.  There's lots of
pro studios and home studios here, maybe if I scare one up, I can have
it professionally done.   Arrgh! why couldn't my dad like the whole
song!  I've been searching for this off and on for about 10 years. 
It's a great song,  sigh...  I thought of garage band too, but I have
no idea how to use it.
These are all great ideas though, you guys rock!
Thanks again.