Okay, this might not work for you but it did for me.
I did quite a lot of research going into my second pregnancy because my first was so disastrous (I have spent days pouring through pubmed), and there were two interesting things that popped up about morning sickness.
One was that it could be related to magnesium deficiency; the second was that cultures that consume raw milk do not seem to suffer from morning sickness.
I checked with my GP and epsom salt baths are fine to have during pregnancy, so long as the water is not too hot. So I have an epsom salt bath every week for the magnesium and use about 100g of the salt in the water. Incidentally, epsom salt baths are supposed to help prevent pre-eclampsia.
There is no way I am going to consume raw milk, but I wondered whether probiotic dairy products might do something similar. So I decided to try drinking Actimel on a daily basis and/or eating some live yoghurt. This, to me, kinda made sense because morning sickness must involve the gut somehow.
Now this is only an N=1, but I have significantly less morning sickness in this pregnancy than in my first -- by a long chalk. I don't vomit at all, and I do not have all day nausea.
When I do get tiny sparks of nausea sometimes, I have noticed that if I drink an Actimel, it goes.
Now I know some of these probiotic drinks contain a lot of sugar, but I was so nauseous last time, I ended up eating a lot of sugary grain products anyway.
The other thing I have noticed is that I don't have any food aversions this time either.
Just some ideas ... the ginger biscuit thing never worked for me at all.