Question: Do you know of an encapsulant material that is Military Grade and can be used on a SOT-23?
Answer: I’m not sure of the question regarding encapsulation, if you are asking for conformal coating, then there are 5 coatings that can be used as they are defined in J-Std-001 page 45, which are:
Type AR Acrylic Resin Type ER Epoxy Resin Type UR Urethane Resin Type SR Silicone Resin Type XY Paraxylylene Resin
You should be able to find the materials you need at these locations.
Now if you are trying to secure components to the board to help with the security of the component to prevent vibration failures, then you would have to use an epoxy type of material and these can be found at:
There are all kinds of product on these sites which will meet the requirements you are looking for.
I will add however, that information on adhesives and conformal coating should be on the drawings and process sheets as these materials should be evaluated to make sure they are compatible with the environment to which they will be subjected to in their operational life.