There is no way to do the transaction in a safe environment as by nature you (nearly always a woman) are locking yourself in a room with someone who is likely larger and stronger than you (nearly always a man) who views your body and emotional output something they can buy.
The people who oppose the criminalization of purchasing sex via the Nordic Model make vague claims about stigma and 'shifting underground' but ignore the reality of the data: The Nordic model has been shown to reduce being hit with a fist (38%) and rape (48%) by significant amounts. Research done by anti-Nordic model researchers substantiates this, while claiming that an increase in reports of verbal abuse and hair pulling makes this a failure. From the report, we also see: “Most of the women who said they would seek help to protect against violence said that they called or threatened to call the police when they found themselves in a dangerous or threatening situation. This would often scare the customers, or others, who were acting threatening/violent away.” There was also an 80% reduction in prostitutes seeking help from emergency care. [1]
Also, claiming that people leaving your borders to break your laws constitutes a failure would be a great way to repeal age of consent laws in the US. Pedophiles just go on sexual tourism trips to places where the age of consent is lower -- but does that make the law unsuccessful?
Even if the law is placing the focus on johns, that doesn't mean that johns are the group that are designed to see the primary effects of the law. The Nordic model is very upfront about trying to minimize coercion, trafficking, and violence against women, and does so by providing exit programs for prostituted women and placing the burden of the law on those who purchase sex.
[1] https://humboldt1982.files.wordpress.com/2012/12/dangerous-l...