I am also a solopreneur as well and also in the process of building an MVP so I can sympathise with your perspective. I am also a trained Business Coach (a management skill I gained 6 years ago), and what strikes me from your particular question, is that your main assumption “2 people are always better than one” may actually be coming from your work preferences.
It sounds like you are an analytic thinking extrovert and that you probably work best in an environment where you get feedback from others which helps you to clarify your thinking? Not all people are like this, many developers for instance are introverts and work best when left alone to solve problems. So if this is the case, the solution does not need to be finding a co-founder, but could just involve you creating an eco system around yourself that gives you the “sounding boards” and human interaction it sounds like you need. This could come from joining MeetUps, to finding a business Mentor (in the UK you can access these through the UK Government Growth Accelerator initiative for SMEs), and even finding a shared work space like a TechHub or Google Campus where other entrepreneurs will be around for you to interact with them for free.
You might be nicely surprised to see how well you can develop your idea without finding a co-founder, and instead bring in the skills as employees as and when needed to fill skill gaps you don’t have. The starting point therefore is the simple question “if you had the right people to bounce ideas off and clarify your thinking around your new business concept, do you think you have what it takes to build a business on your own?”