Source for icon?

[Dan Smith]

I've made a simple launcher for GNUCash in OS X, and want to attach an  
icon to it.  Unfortunately, the largest icons I can find don't look  
very good blown up to typical OS X sizes (gnucash-icon-48x48.png).  I  
assume these images were generated from a larger source.  Is that  
larger image available somewhere?  Or is there another way I could get  
my hands on a 128x128 copy?

—Dan