https://www.smooth-on.com/
These guys make good resins / epoxies, have a gander what they got and look what's suitable for you - I've had a good bit of experience casting 3-4 inch long pieces (mostly fantasy swords) in high detail with their stuff.
You're gonna have to suffer a bit of trial and error though i'm afraid, when it comes to casting small detailed bits worst case though if you're competent at sculpting you will be able to fix the odd little air bubble hole etc.