I'm currently at home because of a rather severe injury (I got a steel truss on and through my arm) and although it's healing very well, it gave me some time to look around on the internet. While updating this website I ended up on my article on Tim's Vermeer’ and as a result I went looking for a Camera Lucida, which I haven't built till now. It turns out that I am not the only one who felt inspired by it: There are now lots of options for experimenting and beginning artists.
So I found, among other things, the NeoLucida, a modern improved version of the Camera Lucida, that you can apparently buy for $ 39,- on their website. Points are that you should look exactly straight down, and sometimes there are complaints that the image plane is very small (I think it should sit really close to your eye, and then that objection no longer counts) and that it's difficult to get used to it. Would not be a objection to me.
Update: there is now also a NeoLucida XL with a much larger field of view. ($ 75, free shipping)
Also, I found another version, the Lucid-Art camera lucida, or else the Lucy. This one is quite a bit more expensive: € 125.- The image plane is a lot larger, and you can place all kinds of filters in it for contrast. Read here for user experiences with the Lucy: drawlucy.com
The cheapest solution, at least if you have an iPad or iPhone, they asked a special app that converts your iPad to such a Camera Lucida. Below the video. Intriguing, but as far as I am concerned, maybe a little too much of a good thing…
And finally another video with the device from the movie Tim's Vermeer:
This goes best with a mirror with the reflective layer on the front, otherwise you will have a disturbing edge to your mirror. Simply take a mirror, dissolve the protective layer on the backside with acetone, glue that under an angle of 45 degrees on a stick and you can paint whatever you see in front of you. Read more in the related article, and also be sure to read what Tim Jenison wrote about his project himself.