If you have the space, the Frequency Central Infinitely Maybe looks interesting. Gives you the option to S&H from something else than noise and you can use the noise for something else as S&H as well.
As for other modulation sources - why the (apologies) crazy 4hp limitation? My favorite is Joranalogue Orbit. It’s 10hp, granted, but it gives a very organic non-repetitive modulation source that I use in every track. I can’t remember a single day where I haven’t used it. I got it back when my Intellijel 104hp 7U was half full but it was one of the core modules that moved over to my smaller 84hp 6U rack that I have used on its own for a while. I couldn’t miss it. I’m sure others here have other larger than 4hp modules they have similar experiences with.
Modular playlist on SoundCloud