Any referrals to a reliable trusted source for 2018 GLC 300 4matic navigation/map updates.

I have a 2018 glc300 4matic. My dealer never alerted me to the free updates and never updated my maps. Now that I am out of warranty and the 3 year free updates are history, they want to charge me something on the order of $500 to update my maps. Ridiculous! They told me that it is my responsibility to know if a map update is available and request the update. Bulls**t! I am hoping that there is a reliable and trusted source for updates that won't cost me an arm and a leg and preferably not a MBZ dealer. My Navigation settings indicates that I have "2018 (V11) North America". Don't know anything more than that as to system.