You're employer or whoever is in charge of the site should know what they require. Generally it's the green triangle they want. Mine are styled like runners, and came from Mark's Work Warehouse for a bit over $100. My sweetie was real happy with her green triangle Blundstones, until she tried the Mark's runners and switched. My last Construction Manager wouldn't give up his Blundies† for anything. Like them, Doc Marten's also began as work boots and are available steeltoed.
†A caveat about Blundies. Polyurethane soles like theirs have been known to develop microbial 'rot' when stored for lengthy periods. Apparently wearing them daily, or most days at least, keeps these microbes at bay, and the shoes wear out as Blundstone says they usually do, in a couple of years of hard wear. The soles can be repaired, but Blundstone will likely be little or no help, if yours rotted away from under-use. Nor will their literature warn you of the possibility. Nicks Shoe Repair on Dupont however will do a nice job.