XPS 13 9370 Charger

The XPS 13 9370 uses USB Power Delivery to charge, and since that's an industry standard, there's much less reason to buy a Dell-branded charger than there was with systems that use the older barrel-style power adapter.  Any USB PD charger than can provide 45W will work, so you just need to make sure to buy a charger from a reliable vendor.  I'm a big fan of Anker and Satechi for those purposes, and here are some options that might appeal to you.  They are all smaller, less expensive, and/or more capable than Dell's charger.

#1: This is a simple single-port 60W charger, available in white or black.  It uses gallium nitride rather than silicon, which allows it to be smaller than typical silicon-based chargers. That also means it's slightly more expensive than silicon equivalents, but it's still a lot cheaper than even Dell's 45W charger, despite being able to provide more wattage: link

#2: This is a dual-port 60W white charger.  It can provide 60W out of either port when used with a single device, or operate in 30W+30W mode when used with two devices.  That can be handy if you also have other, lower-power USB-C devices you might want to charge, although not at the same time as the laptop. Unfortunately this charger can't operate in 45W+15W mode, but it's still useful: link

#3: This is in my opinion the ultimate travel charger for the 2019 gadget ecosystem.  It has a 60W USB-C port, an 18W USB-C port (enough to charge most/all smartphones at max speed, or a Nintendo Switch), and then two USB-A "regular USB" ports.  This is now the only charger I take with me on the road, because I can charge my laptop, iPhone, and Apple Watch every night, and then I still have another USB port for either my USB battery pack, AirPods, or work Bluetooth headset, none of which need to be charged every night.  It's awesome.  And it's about the same size and price as Dell's 45W charger, despite offering VASTLY more functionality: link

Just be aware that with Options 1 and 2, since they're "wall wart" chargers, you'll get less slack from your USB-C cable than you would if you had a Dell-style "inline brick" that had a power cord to the wall on one side and a USB-C cord on the other.  I've found that Dell's chargers typicaly give 9 feet of total cord length from the wall, so I just carry a 10-foot USB-C cable, and when I use it with my Satechi charger, I have even more slack than the standard Dell charger.