So as it turns out it is…weirdly difficult to get shots of Nick Burkhardt’s feet. Not something I ever would have noticed before today.
I did manage to find a few though, and from what I can tell Nick wears full grain or nubuck leather lace-up boots with low-heeled, non-skid soles, in black or brown depending on the rest of his outfit. Practical when you spend most of your time running around on wet pavement or soft, slippery forest floors!
One likely option is these Wolverine waterproof work boots. Though really any good solid-color lace-up work boot would do.
Hope that answers your question!