It may be worth mentioning that Getwebsitesearch is a hosted solution, which costs at least $49 per month. Zoomsearch is a stand alone application that requires only a single payment of $99 and it will do all that Getwebsitesearch does.
Another vote for Zoomsearch. Exactly what I needed, at the price of approx. 2-3 months of a hosted service. Besides, any hosted solution is bound to have downtime at some point, and they tend to be (much) slower. I use the PHP version of Zoomsearch while the index is manageable, and for convenience, but I can easily switch to the CGI version to improve performance when I begin to need it. And licenses are provided on a per-computer basis, so as long as you run the indexer on a single computer, you can deploy search on as many sites as you like. I've tried pretty much every other solution available, there's no better bang for your buck. I understand there's a new release coming soon, which will allow you to deploy the indexer on a Linux machine.
Come to think of it I don't know if a normal search engine would work. We're basically in a niche and the search engine is the main focus of the website. The search engine needs to find different stores or sub domains, instead of finding a certain file. Anyone have any thoughts on this or would it still work the same?