Ergonomic laptop keyboad

I have a long train ride to work so I like to work on my laptop on the
way, but the keyboard on it is causing me great wrist pain. I have no
pain when I use a split keyboard so I'd like to find some way of using
a split keyboard on my laptop when I'm on the go.

I saw the Fingerworks Touchstream, which is kind of what I'm looking
for, but it's hard to find in stock (did they stop making it?) and
it'll be very hard to get used to for me. Do I have any other viable
options? Most of my work is C programming so major bonus points for
standard keyboard layout for symbols like { and \.

Thanks,
George