Have you tried the sources listed on this page (broken link removed) ? Also try the 'I found mine' function on the main part of the cavy cages site as someone may have listed a source close to where you live.
Has anybody tried looking at Ikea for cubes? I'm just curious since I'm looking to build a cage of my own also. Has anybody tried using chickenwire held with cable ties, either?
Was using chickenwire a lot harder than the cubes? I suppose you'd have to make sure to measure it exactly right.. I don't really trust my measuring skills that far, heh.
By the way, I've looked at the online Ikea catalog and can't find cubes anywhere, unfortunately.