Dahua and Hikvision play innovation leapfrog in the budget surveillance camera world. Hikvision ColorVu were the thing to have when they first came out and now Dahua have TiOC and by September we'll all be back on Hikvision no doubt. That Dahua TiOC you mentioned is a very good camera. Hikvision don't have anything as good right now.
As far as I'm aware the only Dahua reseller selling to consumers theoretically is BroadBandBuyer. Just be aware that they require you to set up a 'trade' user account and the terms and conditions are business to business so the DSR doesn't apply and you have f-all consumer rights if anything goes wrong. The idea with Dahua and Hikvision is you're supposed to buy them through an integrator who makes their money doing the install but DIYers want nice cameras too. Dahua may also pull BroadBandBuyer's supply as the 'proper' resellers are having fits over the fact that the public can even see the prices, let alone buy the equipment itself.
If you have issues getting anything, or want a proper trade price, send me a trust message