Managed to get a cheap Master Replicas Force FX Darth Vader 2007 Lightsaber, which is a replica of the version used in A New Hope. Compared to the 2005 Episode V (Empire Strikes Back) version it has shorter grips, chrome sides to the clamp with a lever, and the clamp is mounted an angle. It was cheap due to it not having a battery pack, and also missing the aluminium button on the bulb release plate.
I was able test the electronics using the battery pack from the ESB hilt, so I know they won't need replacing. I did however want to remove the blade so I can display just the hilt on its own, so dismantled it in the same way as the ESB version.
The 2007 version doesn't use a DIN plug, it has a thin molex connector which is inside the electronics housing so was a little more fiddly to take apart, and the blade cannot be reconnected without dismantling the hilt again.
I've also received a button from FenixProps, however it is threaded to fit an MPP flash release rather than the Master Replicas hilt so I've had to wrap the thread in tape so it's a tight fit. At least the hilt looks almost complete now, just need a battery pack or a blanking plate for the hole in the handle end of the hilt.
Unfortunately Master Replicas, or Hasbro who took over the Force FX brand, never released a Return of the Jedi "Stunt" Vader lightsaber hilt in the Force FX range (MR did release one in the Signature series range but when they come for auction they are very expensive). While the "Hero" hilt seen on Vader's belt in the movie is the same as the Empire Strikes Back version, there is a variant shown in the battle scene with Luke (and is the one in Vader's hand when it is cut off) that was modelled on a Graflex flash handle (apparently Luke's saber from A New Hope, which was originally Vader's ...) rather than the MPP flash used in the other two versions. I'd like to add a replica of this saber hilt one day, but while Luke ANH Graflex style Force FX sabers are at high prices I'll have to skip getting one and converting it; I'm keeping an eye out for a cheap option, and will post an update if one turns up.
Dan