It does not sound like you will use it much, so you might be able to use one without a fan. I have some external cases without fans and have not had a problem, but I also have a small fan that I use to blow on the case when using it for an extended period of time. There are some drives which run hotter than others, but I think overall most drives tend to run cooler than in the past. If you don't get a case with a fan, I would not run it for hours transferring data without an external fan on it. It is good idea to check how the case feels every now and then.
I have a couple of Rosewill external cases with fans which I like. it has a USB and SATA connection, which is nice. I don't have eSATA, so I have to turn the drive on before I turn the computer on (desktop), which I do if I need speed, otherwise I can just use the USB interface.Rosewill case blackRosewill case silver
There is a newer version for USB3:Rosewill USB3
It does not have the SATA external interface though, which might not matter to you.
There are many external cases, but I really don't know which ones are best. I got these as they were on sale and looked to have the features I was looking for (fan, aluminum - helps to cool it even with a fan, and SATA & USB interfaces).
Disclaimer: I have no association with NewEgg nor Rosewill other than as a customer.