Accurate micropipettes are going to be kind of expensive. I imagine you want to use the stock 20% solution and then just dilute as you add to the emulsion. I have done this using droppers. 1 drop of Na2 stock plus 1 drop of water makes 10%, etc, etc. You really dont need to be so accurate as to use micropipettes. Of course if you have your mind set on this Van Waters and Rogers is a good source.