There might be a maker's sticker on the top of the fixture. You'll need to pull it down to see though....
Or you could think about updating the lighting fixtures in your house.My parents have stuff like that in a 120 year old farmhouse (not *that* one though).

Go to www.bing.com and type in "Glass ceiling light globes" and look at the first few links.
From the looks of the size of yours, I doubt it is going to be a $15 globe.
Were they there when you bought the house and if so, how old is the house?
Found this on Grandbrass.com. It's called a Williamsburg style fitter. This may not be the right size, but the terminology is useful.
http://www.grandbrass.com/SearchShowItem.cfm?ItemNumber=GLH1022
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Any real lighting stores in your neighborhood? I had an ancient odd globe which was broken. Had another fixture that I was able to take the good globe from and went to a lighting (and electrical) shop. They must have had 500 lights hanging from the ceiling and most of them were on. The 'old' sales person said something like "you have a Model 123454321 made by so and so company"; and, with a couple second pause while he looked up info in the counter catalog rack, said he could have one by Friday and the cost would be $**.**. Should I order one? I was speechless but managed to say YES.
Worth a try.