IDEA for you, t&k (and I love your user name, so creative! envious):
Take yourself over to the Badge Trends thread, and put out some feelers there. One of your sisters may be able to help you out in locating a badge! I did that for a Theta sister a couple of years ago - got her a vintage badge with an interesting history for ~$100 +/-. Not everyone is in the business of making $ or being greedy about selling badges for profit.
Personally I'd much rather see a Theta badge happily shared with an active who will treasure it and wear it with love and pride, than see one go to a non-Theta who will only hoard it (or worse). I am willing to bet this will have a happy ending if you go through one of your own sisters... just an idea.
and, with the holidays coming, perhaps there will be a little $ that you can put towards a badge/pin?