No, Southwire Company only manufacturers their Romex® brand as big as 2 AWG with three conductors and a bare copper ground wire. The most predominant reason being that Romex® cable is only approved for indoor use and as the electrical cables get larger they tend to run outdoors more often than indoors.
Indoor cables such as Romex® are engineered to only be used indoors for cost saving reasons. If Southwire put more effort into manufacturing a tougher jacket that can be used outdoors and also have to be approved for such use than they would be much more expensive. Therefore, Southwire manufacturers MC cable, or Metal Clad for outdoor and conduit use along with UFB cable, or Underground Feeder, for direct burial applications.
If you need a 1 AWG outdoor or conduit electrical cable then you should use MC cable. It has THHN wires as conductors along with a green THHN wire as a ground wire. MC cable has been tested and approved for use outdoors and in conduit in most electrical applications. It’s the most common and cheapest upgrade from a Romex® indoor cable to an outdoor cable.
If your application needs an underground cable than you can use UFB cable as big as 6 AWG or a tray cable for anything larger. In this particular case a 1 AWG electrical cable that needs to be used underground will have to be a tray cable which also comes with an additional bare copper ground wire. The average ground wire size in a 1 AWG cable is 6 AWG because ground wires don’t need the same amount of power as the main conductors of the cable.
If you search around enough you can find a supplier that will cut 1 AWG underground cables to the exact length of your application no matter the distance. In fact, some suppliers bank on customers that want exact cuts because some suppliers, distributors and manufacturers will have either minimum orders or standard spools sizes only. That means you might have a run of 130 feet but you’re stuck choosing between a 100 foot and 500 foot spool size. That doesn’t make too much sense but the suppliers are trying to protect themselves against ending up with short lengths that they might have to scrap down the road.
Search around because there is usually someone out there that will supply you with exactly what you need at the right price.