Yep, that's how you do it.  Look for someone that has what you want.  Someone that's strong in her program, and has worked the steps herself with a sponsor.  Someone who you feel you can relate to by her posts.  Then just email her privately and ask if she is able to sponsor you.  Don't feel bad or rejected if she says no.  Sometimes someone isn't able to sponsor for their own reasons.  If that happens, just as someone else who has the same qualities.  Good luck.