German internet shop Pollin sells a 7" monitor, the LS-7 (or LS-7T as touch version) for very cheap.
At the time of writing, it costs 40 Euros for the non-touch version and 50 Euros for the one with touch. Display resolution is 1024x600, but it will scale down everything up to 1080p. It has HDMI, DVI and VGA connectors so it is a very good fit for the Raspberry Pi, ODROID U2/3 or other small computers. I am going to use it with an ODROID that controls my ShapeOko router. First tests indicate that the inductive touch function works quite well for button-based interfaces, and even using an on-screen keyboard is OK.
The only downside of this screen is that it comes without an enclosure, just the bare electronics. I still really liked the display so I modeled an enclosure in Sketchup. It's a bit fiddly to mount the components but once you have everything in it fits quite well. I had no room to put the composite (CVBS) socket. That is the only connector except power that is not mounted on the main board but comes as a dongle. It needs to be snipped off. But composite video is going the way of the Dodo anyway, right? :-)
The way the display and board are constructed, if you mount them back-to-back like in this case then the DVI/HDMI/VGA sockets come out on top, which makes the display a bit awkward to hold in your hands. So if you want them to be on bottom you need to rotate the screen image by 180 degrees (for example using the XRandR extension in Linux, or AltGr-DownArrow in Windows).
Printing is straight-forward but make sure you have a printing surface at least 20x20cm. Print out the bottom and top panels.
After printing, thread the four holes in the center of the back housing as M4 if you want. These are for fitting a mounting bracket that I will design later. The two tiny holes above and below the five button openings should be threaded for M2 if you have that small a threading tool. I do not, so I drilled them out with a 2mm bit and used M2 screws and nuts to fit the button panel. Thread all other holes for M3.
Mount the button panel on the right with two M2 screws. Plug it into the main board.
Now we come to the touch screen controller. Cut off the isolation on two sides of the fat magnet around the touch screen USB cable. Plug the display into the touch screen controller, it's the small flat cable coming out of the screen. Now mount the touch screen controller with two M3 screws. Thread the USB cable out of the small U-channel in the bottom of the case. I have fastened a cable tie around the USB cable which keeps it in place, so it does not damage anything if you pull on it too hard. Thread the main display cable (the wide flat-band coming out of the display) underneath the touch screen controller.
Now things get a bit fiddly. Plug the display cable into the main board. It's the wide flat-band cable. Since it is threaded underneath the touch screen controller, this is not so easy. I ended up propping the display up in a 90 degree angle. You can see this in the pictures. Push the round black power connector into its hole. It should be a tight fit, but it's a good idea to superglue it in. Snip off the yellow CVBS connector.
Once you have everything in place, push the display into the top housing (careful not to break the glass, it's a tight fit) and mount the top to the bottom using two M3 socket head screws. The top just pushes in; again, this is a tight fit on my printer. If it is sloppy on yours, just glue it shut with some silicone glue so you can take it apart later. If it is too tight, you may want to experiment with the extrusion multiplier.
One more note: There is about 1mm of clearance between the (metal-backed, conductive) back of the display and the main board. I put some tape over the back of the display and the back of the main board to eliminate the risk of short circuits.