I'm stuck with shared internet resources on a boat and I need to pay someone in BTC.

Let's say I have a private key worth in excess of the amount I need to pay. What is the most direct way I can do this?

 A lightweight client like Electrum is an option for me since I do have the ability to run an executable. However, I don't like trusting machines that can run executables without 2 factor authentication like one time use passwords. In addition, it would be nice to be prepared for the time when running .exe's is not possible.

I also don't trust fully online hosted wallets now after MyBitcoin, MtGox and the others.

 I think there's a case for being able to store part of a wallet locally, and/or with one time passwords, and part remotely.

This can be done with a little customised hacking and the paper based javascript wallet system but it's clunky for this application. The main problem is that even if you prepare a load of private keys on a secure connection you then can't divide those amounts offline or online in a secure way without that trusted computer.