This is YrSa's Lovers Lab page:
They have very good BDSM and other animations for download, as well as a list of "required" mods which includes links to a few dildo packs.
Here's the one to a download of Noir and Dark Sims' Double Dong decor set:
This pack is working for me with YrSa's animations, but I haven't tried it on others yet (and the double-dong that shows up is purple, not black, FWIW).
I hope this helps! Let me know if that set works for you.
Also, I would love it if you would link me to the animations you're using. I'm always on the lookout for good F+F content.