It was with a certain amount of trepidation that I've just Googled 'lady's teaser', as I feared that it might be a euphemism for something naughty! However it neither helped with my research nor filled my screen with porn ;-)
Try an email to the Museum of Childhood in London (which is part of the V&A):
[email protected]
and/or the Museum of Childhood in Edinburgh:
[email protected] (including 'f.a.o. Museum of Childhood' in the title).
Maybe somebody there will know something about teasers?