Most of the MSD today are on the slim side, so you should be able to find her a body. Do you have any measurements of the head? They would help to find her a suitable body.
Agreed. Particularly the circumference of her neck hole.
What I sometimes do when I'm considering hyrbidding is I go to
Alice's Collections, look for bodies that I like, and then check the neck circumference to see if it matches the neck circumference of the head that I want to get.
Now Alice doesn't carry every company obviously, but she has a pretty large selection to choose from and it helps me to get an idea of the options available to me.
...In fact, I just went and looked up the Mirodoll measurements. It looks like Yaya has a 6cm neck circumference. While this isn't exactly common, it's not hyper unusual. There are options available to you.
The biggest problem that I see is that you're wanting to body her onto a boy body, which typically have 7 or 7.5cm neck circumferences. But there are a few with smaller necks, including Doll Leaves' 42cm boy (6.5cm), Doll Zone's 45cm boy (6.5cm), and Doll Legend's 44cm boy (6.9cm). With a little modding I do believe that Yaya could fit one of these.
And those are just a few that I found on AC. There are probably other male bodies out there with close—or just right—neck circumferences to what you need.
I hope that this helps and that you're able to find a body for Yaya.