The Girls of Great Britain and Ireland:
Available at Seperwar
or in a smaller version:
Prussian Diamond Tiara of 1913
Available at Seperwar
Diamond and pearl tiara of Queen Maud of Norway:
Available at Seperwar
1910 Cartier tiara:
Available at Seperwar
The Swedish Nine Prong Diamond Tiara:
Available at Seperwar
And they also have come out with popular antique tiaras, like these original star tiaras
Available at Seperwar
and even pieces inspired by films, like the Great Gatsby bandeau tiara
A similar design available at Seperwar
They have many more reproduction tiaras that I have not shared here, including the Queen Mary Fringe Tiara, the Belgium Scroll Tiara and Queen Victoria's Oriental Circlet Tiara. If you do not see them for sale today, just wait...they reappear for sale!
(Disclaimer: I am not in any way affiliated with Seperwar of Ebay. I do not get kickbacks of any sort. In fact, they probably wish I would stop emailing them with wishes for tiara designs.)