Used to be available in Caesar Clifford's website, along with some other scenarios. This one's a great exercise in a rapid prosperity push because of the time limit. I've played this before and I'm thinking a fun additional challenge would be to build one of each patrician house.
There's a CC Swallowdale thread in the forums with a review of the scenario.
If you want a similar challenge without the pressure of a time limit, you can check out the scenarios Whitby and Capreae.
Welcome old friend and proconsul of Rome. I trust you are well and looking forward to that which I have for you. I have a special task for you. One which I wouldn't trust to anyone other than you. I want you to go to a land called England in Britan. You have heard of the visit of that remarkable man Arthurous Ransomous. He brings tales of a hidden valley in this England called Swallowdale by the natives there after one of their small birds. My children have been delighted to listen to his tales so much that they want to visit it. I can't leave Rome for a few years but wish to take them there to see for themselves.
Arthurous says this is one of the great places for children. It has everything that they could want. But I, old friend want more. When we get there I want palaces built that we can stay in and all the trappings of a fine city established. When you complete this task and return, I will leave you in charge here in Rome, my old friend. So you have a prize you would never have dreamed of before.
I want you to send many items from Swallowdale while we wait for you to prepare it for us. Especially fish as we have heard so much about the fishing there. I however do not want you to spoil the valley with mines and the like. Maybe one mine for weapons but nothing more. However much I trust you, I will make sure you do not do this, old friend. I also don't want a massive city. Just enough to provide the luxuries that I require when there. Do not hassle the natives. We will leave them alone and they will leave us alone. However Arthurous was talking about Picts and Martyrs, so you had better be a little prepared for some fighting. I have not heard of these but I dear say you will find out what he meant.
This will be a great holiday home for our family. Do not let me down, old friend. The rewards are great for you. Failure does not bear thinking about. Oh and hurry, you do not have long. We wish to go soon.