Welcome. I looked into Lexapro once myself and found out too that there's no generic. Not sure why. Maybe it's too new and the patent hasn't worn out?! Whatever the reason, if it worked as well as it did in the past for you - then hopefully it'll work well for you now. Why mess with what works? I know name brands can be expensive, but you're health is too important.
Congratulations on being pregnant. (I'm assuming that you are the one who's pregnant). I'm not a doctor, but is this your first child? I wonder if the change in hormones and stuff which you may not be used to (not to mention the stress of being a new mom) could be part of why your anxiety is coming back now.
As far as finding a therapist... If you're using insurance you might want to call them to find out who in your area is covered. You can always look for referrals from friends, family, online, etc. and then call the insurance company and ask about an individual therapist or just call them and they'll give you whoever is closest and covered. If you're paying out of pocket (on your own) then yeah... you can just call someone up and ask if they're accepting new clients. Some therapists have websites where you can get a feel for who they are and their approach to treatment, but many good ones do not. You may want to also consider social workers who are similarly qualified. But whether it's a social worker or a psychologist they should be licensed in your state.
When you call expect to have a 5-10 minute conversation about what you're dealing with and whether or not they can help. Therapists, like doctors often have areas of specialty so you can ask if they have experience with anxiety like yours. Also I'd ask about anything else that might be a dealbreaker for you (for instance, if you have to have a therapist who speaks another language, is of a certain race, gender, faith, etc.). Remember that although it's a professional relationship, it's still a relationship and you'll be sharing a lot about yourself so the most important thing is to find someone you feel comfortable with. It's OK to try someone for a few weeks and give them a chance and then decide to see someone else. Good luck!