We now have a new lamp, for $12 and change, from Wal-Mart to replace the one that melted its shade last night. I hate to replace instead of fix, but at $12, I'm not sure I could even get a replacement diffuser. Finding a way to replace the diffuser cost-effectively is now a low-priority problem.
We are also the owners of a new Dyson DC14, which I haven't unpacked yet. It's the "Full Kit" model, which appears to be packaged specifically for Costco, and as far as I can tell, it's about equivalent to the Full Gear version without the bundled cleaning products. We paid about $100 less for it from Costco than we would have paid Linens'n'Things for a comparable model.