NavList:

Most of aircraft bubble sextant, such as A12, A7, Mark IV, etc. already come with a tripod adapter that can be connected to a regular photography tripod. You might have to buy a little longer adaptor available online.  

In my experience, the use of a tripod does not significantly improve the sights accuracy, but it is useful when taking meridian passages (of any celestial body) where small altitude changes are critical to get the transit time and therefore to obtain a reasonable calculated longitude.