Hello Chromedome and welcome to the site.
We have used Soya milk for years, even before prostate cancer, and it really doesn't work in coffee, Yuk!!
Perfectly acceptable in tea though. (No curdling)
We only used organic Soya, which is Tesco's own brand and it's about £1.18 a litre carton.
As far as a Thermos is concerned, then perhaps you could take a separate container for the milk, a bit of a faff I know keeping it cool in the summer.
I drink my tea black so not a problem for me!!
Goat's and sheep's milk, though not dairy, are still animal products as far as I'm concerned but if there is a dietician among us perhaps they can say whether it's the makeup of these products that makes them safe.
(I'm not a vegetarian, in fact I've just eaten a chicken curry, I just don't like milk in my tea.)
Anyway, here you are among us. We are a very friendly bunch of people, all prepared and willing to help with any queries you may have, on whatever aspect of Prostate cancer you may wonder about.
Nothing is off limits. We share experiences.
Sandra