My solution is a cheap lock and a cheap bike (and inexpensive touring gear). I don't leave anything unattended that I'm not prepared to have stolen. After the nice bike my wife gave me as an engagement present (37 years ago) was stolen from its parking spot at work, I don't trust anyone, and don't buy nice bikes any more. (My current bikes were given to me in return for favors and work done.) When I tour, I have less than $800 tied up in the bike and gear left unattended. That's less than the overall cost of my typical tour. A theft would mean a change in travel plans, then the need to scrounge up a new kit.