and am really not impressed with the Nightstick -- but I'm at a loss for what my options really are.
What's wrong with the Nightstick? It's made by SuperTrapp, they're a well-known exhaust maker who's been making 'em for decades. And, as you likely already know, it's legal in CA, where most mods (like the K&N or V&H air intake kits) aren't.
I'd ask at your local dealer. Now, granted, they're almost certainly going to try to sell you whatever they have in stock, but -- it seems reasonable to me that they've likely faced these questions before, probably many times before, and they know what's legal and what isn't.
From what I've looked into, the Nightstick and Screamin' Eagle intake are 50-state legal, and even the SE ProTuner can be configured to maximize the tune to whatever's allowed under California law.
For V&H, they have a specific website set up to address what's legal in California among their product offerings, Vance & Hines California Products Guide
. I can't figure from there whether they're saying it's legal or not. I mean, it says "no exhaust systems qualify for CARB replacement parts," but then it does bring up the Competion Series slip-on, but then on the product page it flatly says in a big red box "FOR CLOSED COURSE COMPETITION USE ONLY. NOT INTENDED FOR STREET USE." So -- I'd say you'd have to call 'em and ask 'em. I'm pretty sure their VO2 is not legal in California for street use; it doesn't show up in their California products website at all.
For K&N, the AirCharger 63-1130 is definitely not legal in California. The HD-4915 replacement filter may be legal; it appears to be sold under Harley's own brand as well and there's no indication on either K&N's or Harley's site that it would be illegal in California.