Welcome to our forums, wired!
Niobium is most likely available in wire form so a box clasp is not a usual product. Titanium is sold in sheet form and could be worked into a box clasp. Lobster clasps are usually made by casting the components. Some shapes might be stamped. Because of the metals' nature, Titanium is difficult to cast. I'm not familiar with any vendor who has box clasps or lobster clasps in either of these metals.
If anyone has them Reactive Metals is the most likely place.
Wait.... I spoke too soon. The Ring Lord has titanium lobster clasps. Scroll down the page at Titanium Lobster Clasp to see their offerings.
Titanium and Niobium can both be colored and are both very UN likely to cause allergic reactions when people wear them.