Haha, I was actually about to drop a disclaimer , but I decided that everyone would realise that I was kidding (or was I ), and if not I'd make that clear after someone asked me for details on making it .
As it seems you are woried merely about destructive resistance and not pick/bump resistance then a lock like this one is what you are after, i'm thinking more the shape than this specific lock. The shrouded shackle stops bolt cutters and prevents hacksaws to an extent its also a strong weather resistant lock. With all of this however remember if they can't cut the lock they'll cut the chain so make sure that your chain is also up to the abuse always lock up the back wheel of the bike and you should be ok... being a hobby picking forum few people will have specific figures for how hard the shackles of locks are. Company specific sites often give info about physical resistance, such as this "Chrome-nickel-molybdenum alloy steel hardened shackle, tempered and nickel plated.
Bolt-Cutter proof and lever proof shackle protector." Up to you to inturpret the sales bumpf. Good luck with the bike.
, but I decided that everyone would realise that I was kidding (or was I 
), and if not I'd make that clear after someone asked me for details on making it 
.
