Try a Dunlop Rotovibe, they're awesome for the leslie stuff. Capable of really thick warpy sounds or anything under. I prefer it over my Univibe because it's capable of extreme warpage. It's awesome as a subtle effect too for adding a warped sound to your rhytm or lead, a la Jake E Lee or old Zakk Wylde. The only downside is as soon as you turn it on you're on full effect mode. Seriously though, I've tried so many rotovibe style pedals (minus the H&K mind you) and the Dunlop was my fav.