SkySafari, the star chart app I use on my iPhone (and an all around find product, in my experience) has quite a few lists of objects that come with it. Unfortunately, none of them are a list for the Herschel 400.
Never fear, though. You can import and export observing lists with SkySafari, and I’ve built one for the Herschel 400. There’s one object that’s left out because it’s a dubious duplicate of another object on the list, and the total objects on the list is a little over 400 because there’s a few objects on the Herschel 400 that have multiple NGC numbers that I included, but other than that it should be accurate. It took several days to plug all the objects in, but now you don’t have to. You should be able to just click on the link below while using your iPhone or iPad with SkySafari installed (I’m not sure if this will work with the Android version or not) and you’ll be good to go.