Any hobby store, particularly for models and such, will carry Insta-cure+, gap filling super glue (cyanoacrylate). It is inexpensive and made for uses in spanning gaps in sculpting and modeling, like you might have gluing the leg back on. It is also sandable and comes in different dry time options with different levels of viscosity. I have used the purple cap option for years. Good luck!
ETA: In case I wasn't clear, I sculpt exclusively with Apoxie Sculpt and Apoxie Clay and this is what I have used for similar problems to what you are experiencing. It will not erode or damage the Sculpt.