Shuttle in Switzerland

Ruth, sorry but I don't have a recommendation for shuttle services. However, I'm sure there are handicapped residents of Switzerland who ride public transport so don't be too quick to assume that just because you're handicapped that you can't ride trains.

https://www.sbb.ch/en/station-services/passengers-with-reduced-mobility.html
https://www.sbb.ch/en/station-services/passengers-with-reduced-mobility/faq.html
https://www.sbb.ch/en/station-services/passengers-with-reduced-mobility/sbb-call-center-handicap.html

Shuttles are not really a Swiss thing. People use public transport instead.
There are some, they advertise in English because their market is North American travellers who think that is the way to travel. They are not cheap.

May I ask what your "handicap" is? Are you slow walking, use walking sticks or are wheelchair bound.

I agree with what Tim says, perfectly possible to get around by public transport with a wheelchair. I see people in wheelchairs on trams and trains all the time. Sometimes you have to book in advance, because there are 1-2 steps up into the train, modern trains have level access. All new trains must by law by wheelchair accessable without assistance,

"chalet in Lauterbrunnen" - is it actually in Lauterbrunnen or above it? If the latter, does it have road access (some don't)?
"Radisson Blu in Zürich" - is that the one at the airport, or in the city centre?

You may want to reach out to your cruise company - they may have agreements with a shuttle service already. Most river cruises provide shuttles to the airport, so they may well can hook you up with the shuttle to Lauterbrunnen.