I miss being a wife as well, and I'm also very introverted and have no idea how I'd meet someone, and if I did, how to flirt without looking like a bozo!
So, for now, I'm stepping out in other ways-- getting my kids involved in a community organization where I might meet people (probably all married, but they might have single friends) and joining a singing group (which is mostly women, but they might have single male friends!). I'm just working on my social development outside of work and home, and seeing where it goes from there. I figure that the more I focus on an "I want a relationship" mindset, the more unhappy I'll be, and that will make me less healthy and less open to the right relationship (and possibly open to an XWH Part II).
If it helps, I had my kids at 29, 31, and 33, but I am on the YOUNG side in my groups of friends when it comes to having children. Most of my friends either started in their mid-thirties or are starting now in their late thirties.
And my brother is 44 and has a 17 month old baby and another on the way (and these are his only kids).