A note before recommendations: all bike locks can be defeated either by picking or destruction. The most important function is to slow the theif enough to make it not worth their time.
That being said, Kyrptonite makes a good line of bike locks.
Heavy chain (with a sleeve to protect your paint) and a sturdy key lock.
Stay away from barrel style key locks.
My recommendation is to get something that takes more that a normal pair of bolt cutters to defeat (think more than a 1/2in chain). You will never have one large enough to beat a grinder, but you can make it difficult for them.
The more secure the lock the heavier it is going to be, so that’s a thing to keep in mind if weight is an issue.
there is a bike lock made to wear down grinder disks such that they would have to use something like half a dozen or a dozen disc swaps to cut through.
Yes, but most of the are not practical for bikes, or are prohibitively expensive ime.
yeah I have not gotten one but one of my rules is buy a more expensive lock than bike so I might at some point.
Which lock is that? And that is an interesting rule!
yeah sorry I was heading out the door when I first made the comment. Its been awhile since I saw it and this looks like kinda one https://www.amazon.com/SKUNKLOCK-2-Carbon/dp/B0C44WFRWC but honestly I have seen better performance in videos. Like many many discs being destroyed. carbon does sound right as the material that does it and curiously they have another thing that apparently realease irritating chemicals but honestly while kinda funny and satisfying sounding does not seem as practical as the anti grinder one. Not to mentions it says under pressure so im sorta wondering if it could accidentally be released like in a crash. Honestly the price for the carbon is not as high as I remember and certainly is in the realm of what I go for. To me its get a refurbed bike from something like working bikes that also goes to a good cause and slap one of these on it so it will cost the thief more than the bike will ever get them if they are lucky enough to not get caught with all the time it will take them.
Abus (German), Kryptonite (New York), Viavelo (Canadian but has GoDaddy domain) were the closest I could find.