We partnered up in our belly buddies group. As it turned out no-one announced DS's birth so I ended up doing it myself
Just pick someone you feel comfortable with & someone that you know will follow through with it, I know when mine didnt follow through I felt invisible or maybe not good enough as I had done theirs, you dont need those extra feelings just after you've had a baby

Good luck! There are lots of lovely ladies here to choose from!!