Some websites like Godaddy can act as 'brokers' wherein they will contact the owner of that domain that you like and then negotiate with them on your behalf (they will get a commission if the negotiation turns out to be successful). This is clearly a costly process but if you really want a certain name for your blog's branding, it doesn't hurt to give it a try. Just take note that in most cases, the original site owner might refuse to sell their domain, and the fees you paid with the broker are often non-refundable.