I haven't seen one either, and believe me I've looked.  Assuming you meant to write Latitude 7490 rather than 7940, the power requirements of those two systems would require a charger capable of 110W total output.  That would be a physically large charger, much too large for a reasonable "wall wart", so it would have to be a brick, rather like a regular laptop charger.  If you've ever seen regular laptop chargers with 100W+ output, that would give you an idea of the size you'd be dealing with.  So packaging is probably a limiting factor at the moment.  Cost and the relatively small market of people with two USB-C laptops today is probably another.  For what it's worth, I just bought a Nekteck 65W USB-C charger because 65W covers most Dell and Lenovo laptops, the price was right, and it's USB-IF and UL certified, which was important to me given the widespread issues around some USB-C chargers not long ago.  It came with a 6-ft power cord, but since I realized my regular laptop adapters all gave 9ft of total cord length from the wall, I also bought a Nekteck 10-ft USB-C cable.  If you also want another cable, make sure you use one that's rated for up to 100W (5A) if you want the full 65W.  Normal USB-C cables are only rated for up to 60W (3A), and if you use a cable like that with this charger, you'll only get 60W.  That 60W baseline for cables incidentally is partly why there are relatively few USB-C chargers that will do more than 60W.

Hi jphughan, thanks for the reply. I did mean 7490, my bad :)

Thanks for your input, I'll have a look at the charger you mentioned. 

Dan