There are a couple of misconceptions in your question.
First of all, sone does not translate to dB. Not in any way. Sone is a psychoacustic figure that tries to model the amount of discomfort caused by noise. Louder noise at other (usually lower) frequencies, or even the same frequencies with different harmonics may very well have a significantly lower sone rating.
dB on the other hand directly corresponds to the signal strength, i.e. how much energy is in the sound wave. This may not be what is causing discomfort, but it is what is decisive for whether hair cells are damaged or not, and how fast (which is what causes hearing impairment!).
The statement "hearing protection is necessary at these levels" (104-110 dB) is wrong, too. Hearing protection is necessary at much lower levels already.
The important difference between sound levels in the 80-90 dB range and levels in the 100-110 range is that you can (occasionally) support one for minutes without taking permanent damage whereas the other will cause permanent damage within seconds.
For long-lasting exposure measured in tens of minutes or even hours (such as you will have over an afternoon of woodworking), hearing protection is not optional or something that is only needed at the highest level of noise.
With that in mind, it actually becomes somewhat unimportant whether a machine has 90 or 95dB. You need hearing protection in any case.
Now to answer (or trying to answer) the question
At least in the EU, there exist many binding restrictions for any kind of machine or tool, both on the allowed amount of noise emission and it is compulsatory to measure and document the actual levels. There are several different regulations for inside and outside work, and for hobby and professional work, so overall it's so complicated that an average person without a degree in law can't be sure.
For example, my lawn mower must comply with 2005/88/EG, which says that it may not exceed 80dB, and it must have a sticker with a certificate that says it doesn't. The concrete compactor used at the building site down the road, on the other hand, is allowed to have 110dB but may exceed that exceptionally and doesn't need a certification sticker, although it is equally used exterior (but it's a different class of tool, and for professional use).
Also, since the noise level depends on what you feed to a machine, some machines will only have a "typical" or "idle" noise rating, to which you can add at least 10dB if not 20dB when in use.
In practice, the information can be hard to find (you would expect to find it in the data sheet or the technical safety instructions of every product). However, you can usually find the noise rating if you invest a little time looking. Cheap manufacturers will only do the bare minimum required by the law, better manufacturers will give you two ratings, one when the machine is running idle and one when it's cutting through wood, and some will specify an error margin (typically 3dB).
For example my dust collector has a rating of 71dB +/- 3dB, my plunge router is at 93dB +/- 3dB "under typical conditions" (it depends on what kind of bit, and what kind of wood you use). That is about the same noise level as usually specified for a processional grade planer running idle.
Some manufacturers seem to have found a legal way to avoid openly publishing the noise rating (for example, there seems to be no way to find a noise rating to the Mafell Erika series, which is the single best known professional grade pull-push saw -- other than owning one and crawling under it to read the little sticker on the bottom).
So, to summarize, while you will maybe not find a rating for the one machine that you are interested in, you will surely find a rating for a similar machine, which will be roughly in the same ballpark.