Thanks Thaha.

I got one Law firm at CA, http://www.patnaiklaw.com/index.html

The lawyer was informative and she actually can answer your questions over the phone. She told me that its important to have H1 receipt/ approval notice from USCIS. However she can still help you with transfer in case you only have the receipt number (when your employers doesnot give your I 797). But the latter case could face rejection from USCIS. She said she actually has done one transfer without H1 documents. She can work directly with employee or employer.