You mean Clark's of England
? They're the ones who make the Wallabee and the Desert Trek. I've never taken a close look at Higgin's shoes, but it would be entirely in character for him to wear either the Wallabee or the Desert Trek. (It seems to me that it's part of the British expatriate standard costume, along with the khaki pants and the pith helmet.)
You can buy their shoes all over the world, but the most convenient way to get them in the US is Zappos.com
In college I wore the women's version
of the Wallabee shoe for over a year, until I held them too close to a campfire and the soles started to melt. They were my favorite pair of shoes ever. Sadly, they were less available back in those days, and then they went somewhat out of style. I see now that they've made a resurgence, and I've been thinking about buying another pair for myself.