I looked into this myself around maybe two years ago. Amazon had a couple of third party receivers that were less expensive than the Canon, but their reviews weren't so great either.
The best results I recall reading about were from people who had dedicated hand-held GPS units, the kind sold for hiking and hunting. They were accurate and reliable, but they were similarly expensive and required you to do a post-process to export their tracking data and add it to your photos.
One option is to try the Canon GPS first and see if it works for you. It's available to rent at Lensrentals and the price is reasonable, and that way you can form your own opinion. Link
My 7Dii has a built-in GPS receiver but I haven't been impressed with it. It won't lock at all indoors, and even outdoors under relatively open sky I've found it to be pretty finicky.
The solution I use is an app on my phone called GeoTagr. It costs $5 and uses the phone's GPS to track your position during the time that it is active. Afterward, it will produce XML sidecar files with geolocations for your pics based on their timestamps. I realize this is a manual post processing step which you said you didn't want, but it's a lot cheaper than the Canon GPS module. GeoTagr is only for iOS, but there may be something similar for Android.