Promethazine is also another sedative-antihistamine, although it's quite weak so it may not be appropriate for your cause.
I think it's great that you're so cautious when it comes to benzos, and looking for a natural alternatives is definitely the right move, but I should just mention that 0.5mg Clonazepam is a
miniscule dose! And if it knocks you out completely + no grogginess then it's doing it's job. Well. You are right about dependence, but sometimes perhaps it's worth it...? I mean, definitely try the alternative route first (Valerian is actually also very good), but it the sleeping is still a big problem then maybe just stick to Clonazepam. If it really hits you as hard as you say it does you could probably break the pill down the score marks and use just 0.25mg daily!
I have chronic insomnia and I have been on 6mg Clonazepam daily for the last 2 years of my life. In those two years I have gone for a week or so without them (waiting for a refill prescription) and never have I felt the need to up the dose. In two years it doesn't seem as if my tolerance has gone up. Clonazepam is one of "best" benzos, IMO, because you are less likely to become addicted or dependent than with others as it has a very long half-life. Diazepam (Valium), Alprazolam (Xanax), Temazepam, Nitrazepam, Midazolam, Zolpidem, Zopiclone - I've been prescribed them ALL in the past; and subsequently found them ALL to be addicting and raise my tolerance very quickly, especially Valium and Xanax (which actually make me few sooo groggy the next day). Technically, I am physically addicted to Clonazepam (2 years of hard use and 'technically' I have to...) but I never
feel dependent on them.
I'm basically just saying that - if the natural/supplement route doesn't help - it really isn't the end of the world if you start taking 0.25-0.5mg of Clonazepam at night to aid your sleep. You might even find that after a while of 'co-sleeping' you may just get used to it. You say your sleep is fine 90% of the other time, so perhaps this is just something to get adjusted to. Anyway, here's a list of things I have found helpful for sleep (I have tried almost everything to try and synergise with Clonazepam, 'cause that doesn't - nor has it ever - helped with my insomnia):
Valerian Root (get concentrated tablets = less grogginess)
Passion Flower (Passiflora - be careful, though, as it has MAOI action)
Kava Kava (I found more addicting than Clonazepam, and it also has MAO-B inhibiting effects)
All the sedative-antihistamines mentioned here (Diphenhydramine is probably the strongest, but has somewhat of a "hangover" effect in the more", plus you can get tolerance)
Phenibut (addicting and expensive, but works)
GHB (obviously I can't actually recommend this, but it works. Doesn't give you proper sleep though; it's not restorative)
Hope this helps