You have a search engine right? So, for a fixed period (say 1 year) have a set of sponsored results solely for websites that link to or have a SNAP search box. Webmasters want more hits from search engines - you can give them that at no cost - in return you get traffic and brand building from them. Anyway - you can't really buy much for $250,000 - a proper national launch would need at least $10 million. So why not just do it for free? :) Oh, and policing this is easy - you just make sure you spider the webmasters' sites frequently to ensure the code is still there.