The main challenge was to build it with easy to find parts, but the lens is a problem. I had a pair of perfect lenses (the lens on the right. A plan convex lens with a size of 33mm and a FL of 100mm), but these are difficult to find. In China I had the possibility to buy them by 100 pieces min. order.
So I took the weekend for a few optical tests and the winner is.... the lens of my magnifying head glasses. There are 3 lenses in the set, but the one we need is the big one with a magnifying of 3,5.

The frame of these head magnifier will be used to hold the data glasses.

And the price of the whole thing is about 10$.

It has a focal length of 12cm so that the way from the screen to the lens will be 8,1 cm, with a magnifying factor of 3,. On picture 2 you can see how I found the focal length.