Generally, does travel insurance cover death? (I mean such that the beneficiary would get a lump sum, €100,000 or whatever you signed up for, in the case of accidental death while on the holiday.) If not true in general, is such a thing available at all and if so, where can it be found?
Yes such insurances exist. However you didn't say where you are located. If you simply want an example I can point you to an example in the Netherlands (link is Dutch). They cover
Per verzekerde (overlijden/blijvende invaliditeit) € 5.000/€ 50.000 Als gevolg van besturen van motorrijwiel (overlijden/blijvende invaliditeit) € 5.000/€ 25.000
If you die your relatives will get 5000, if you get permanently injured you'll get 50.000. Again to get this insurance you need to live in the Netherlands.
Maybe you can combine such a travel insurance with a life insurance?
Some Travel Insurances do cover death. However it's likely possible that not all types of travel insurances cover it.
For some personal experience, my travel insurance covers a large amount in case of death, but my insurance is a student travel insurance valid for one year.
In case of smaller duration of travel, it's probably unlikely to be mentioned separately but I am certain both kinds of plans are available.
As of now I'm unable to find specific examples for you because that depends on a couple of factors such as your citizenship, country of travel etc.