Here is a link to one supplier. It is not a recommendation to use them, it is shown to give an idea of the price. There are a lot more online that may suit you better.
Hi,
Here are the specifications for a HP 430/431 Notebook.
It shows that the maximum RAM is 8GB over 2 SODIMM slots, i.e. 2 x 4GB DDR3 PC3 10600 1333MHz.
http://h20564.www2.hp.com/hpsc/doc/public/display?docLocale=en_US&docId=emr_na-c02822281