May 16, 2016 - 1:44 PM
The difficulty with the Swiss Half Fare Card is that it's slightly different from the Half-Fare travelcard for Swiss citizens when it comes to trips to other countries. More details are on the Swiss Half Fare Card page. I think you should be able to book this on the SBB site and pick the domestic version of the card, but I am not 100% sure. An alternative is to simply book a regular ticket to Brig through any of the sites listed here, and buy a 50% discounted ticket Brig - Wengen in Brig or on the SBB site (I think you need an account for that). That does not take a lot of time as you can get it from any of the ticketing machines, provided that you buy your Swiss Half Fare Card in advance and print it at home (see here). Note that the ticket for the Italian leg must be bought in advance as most trains require seat reservations. The reservations will be included in the ticket.
If you get off the train in Brig you can take the opportunity to proceed on the local train via Goppenstein to Spiez, which is far more scenic than the fast trains through the long tunnel.