Since the last vulnerability in a hardware wallet the general confidence in them has fallen significantly (also mine, so maybe it's just my feeling).
I think that you should read this thread, it's not long.
At the end there are ideas for air-gapped cold wallet; if you are a little bit technical you can even go for Raspberry Pi.

And here's some more to read. Sorry if this scares you, but if we talk about big bucks you better get well informed.