Although it's good to always try the OG community first, have you looked at ebay and craig's list? I found a few decent lamps (although not lava) at local 2nd hand shops and yard sales!!! Keep your eyes peeled!! You just never know where lava will show up, lol!!!
I'll second what Carol said. Although I've had zero luck with Craig's List, I've scored a few beauties on ebay. (Been burned a few times too, but it pretty much evened out.) A lot of times it can come down to timing - i.e. seeing it before another community member sees it!