I had one of the 'Irvine/Irving'? style jackets a few years ago. It was so good, I couldn't wear it unless it was minus five outside!! I ended up selling it and buying a less toastie leather.
The
genuine Irvin jackets are now available in a lightweight version.
If you get a sheepskin jacket, don't you think there';s a chance that your bottom half will get cold?
There are matching trousers available, although I don't think most people bother.