Steve Losh in his already-classic CL blog post [^1] suggests either Vlime or Slimv, quote:

„If you’re like me and already have Vim burned too deeply into your fingers to ever get it out, I’d recommend Vim with Vlime. It will give you 80% of the experience you’ll get with Emacs.”

If you want 100% of SLIME goodness without sacrificing vim, try spacemacs [^2]. I switched about two years ago and am very happy.

[1]: http://stevelosh.com/blog/2018/08/a-road-to-common-lisp/#lis... [2]: http://spacemacs.org