The biggest restrictions on detectors are likely to be the light intensity, and the size of one pixel.
The intensity of light that comes through the slits is actually quite small. After all, the slits have to be narrow in order to function. Then you need to go to the screen, spreading out the energy over a wider area. Next, you want to cover the range of intensity in order to see the shape of the pattern. So you need quite a range of sensitivity.
To get details of the pattern, you will want a fairly small size detector pixel. Smaller area means you need more intense light to get signal.
A suggestion: Are you skilled enough to get and install something like a CCD from a digital camera? Probably you don't want to get an actual camera and take out the CCD because it will probably be pretty small for your purposes. To say nothing of destroying the camera. But there are various sizes of CCD devices. And they can be quite sensitive. And they come in a nice grid pattern so your data is automatically divided into locations.
A quick Google found a bunch of things, but I'm not sure where you want to go.
As well, you want to exert care with the light source. Monochromatic is necessary. Intense is good. Consider something like an LED laser pointer type device. You can get them for cheap. Possibly you can get a lens for it that will spread the beam out to the width that is most useful for your experiment.
Alternative: Instead of having the detectors directly receive the light, you could have the light fall on a screen. Then you could use any convenient camera to record the image. A few clever tricks with marks on the screen could give you calibration distances. Then you could extract any information you want from the camera image.