need a new lid/top for my midnight century lamp...

[torpid tapir]

the lamp was knocked over during one of our cats' spastic moments, and though nothing was completely broken, the plastic lid did crack.  fortunately only a tiny bit of the fluid leaked out; however, i need a replacement lid now and the lava lite company says they don't have any.  :/

 

the lamp in question is a midnight century.  it doesn't have the sort of lid that just sits on top of the lamp (with the lava inside being secured by a bottlecap); it has just the screw-on lid and nothing else goes underneath it.  i'm to the point where if i can locate a jar lid that will fit the tread, i'll just put that on there and paint it black to match.

 

any ideas/advice?  i want to run my lamp again.  :(