I have now gone from zero lava to 5 in the space of three weeks....found a 32oz from 1995 (alas, red) yesterday drove 10 miles to get it paid 15 bucks.
I've bought one full Mathmos Astro lamp and two extra globes from Electric Plant. Three serperate orders. All items arrived prefectly, my credit card was charged appropriately, and I couldn't be more pleased.
If you want a new lava lamp that works - you can't beat Mathmos from Electric Planet. It's pricey, but worth it IMO.