Best in my opinion would be a pair of redwing work boots. I would go with a “6 as they are better for working in tight areas.

I would also recommend getting his feet properly sized for the new boot as they can be rather pricy.

Being a Canadian sheet metal worker I found it was practical to have two pairs of boots one for summer and one for winter.

Hope this helps

A couple of questions first. Are we talking commercial, industrial or residential? Do the boots need to be steel toe? And lastly what part of the world are you in?.