I just found the The "Cycle Club Junior" at my local Big Lots store for 6 dollars. I bought one on impulse and tried it out. I'm going back today and try for a second one. I foresee a need for making a two link chain out of these. A sticker on the package will inform you that all special offers and warranties are null and void. I'm still going to try for the second one. These are heavy and that's a good thing when it's a bike lock. I found this in the "hardware" department aisle. Did I mention they are heavy? This is a closeout, liquidation opportunity, short lived for those needing security hardware.

I have 2 full sized versions and they do a pretty good job.
I did have one lock "stick" closed once, though (key turned but lock didn't disengage) and that was pretty nasty...had to carry the bike 1.5 miles home (glad I'd only made a short errand run).
I destroyed a couple cut-off wheels then finally unstuck the locking mech by tapping it with a hammer.
So, yes, they are tough...but lube the locking mechanism every once in awhile.

That's good advice and is applicable to any lock. I found that white grease in the spray can (blue) is the best for keeping locks working.