Hi there,
Interesting question, I am a BA Manager, who made his way up the ranks. I did a number of projects where I worked as both the BA and PM.
The answer to your question is thus:
1). first of all have you considered a BA Managers role?
2), I have hired both BAs and PMs. I don't look first of all at what certificates you have. I look for your experience. Most hiring managers that I know are the same.
3). Don't make the mistake of thinking just because you have been a BA that you can or will like being a PM. They are two different roles. That said, I have in my time worked as both.
4). You haven't said, but do you know how to be a PM (be honest), but just don't have anything on your CV to say that you do?
What I would do in your shoes is ask if you can work as a PM on a small project - one that they are happy for you to be a hybrid (A Hybrid is term used by Management and Employment agencies where the employee acts as both a BA and a PM). The best people to ask would be however is in charge of your Project Portfolio.
I assume you are a perm employee of your company? If so, have you spoken to a HR member about what options you have? You never know, there may be a possibility but that isn't currently advertised?
I personally wouldn't worry about the Certificates until you have tried it. You may not like it. The alternative of course is to look elsewhere - outside of your current employers?