I would say travel industry experts first. Based on what you have described, it sounds like you need to figure out what the market segment within the packaged travel/tourism industry that can benefit from your product. Then look at your competition in that market segment and see how they sell the...
That's a much more complicated question than it appears to be, as there are multiple sources which will get you some of the inventory, but nothing which will get you all of the inventory. If you look at an OTA, they are pulling from typical sources like SABRE or Amadeus, but also from what is in ...