Maybe use your current system with a rolling password, so that the previous password no longer works? Obviously that would take a little feat of memory, or at

Maybe use your current system with a rolling password, so that the previous password no longer works? Obviously that would take a little feat of memory, or at least some kind of prompt, but you could memorize a poem or something and use that - it would prevent replay attacks. Or, use an algorithmic password, perhaps one where you do a sum based on the time of day. All these solutions require some level of coding sadly, but I would have thought it would be something a freelancer could knock up relatively cheaply.