This guy Les put together a piece of software to view/calibrate a spectrum[0]. He also has a YT channel[1] where he builds a couple RasPi spectrometers using pre-made spectroscopes that run $50-100, but the whole package is a lot more compact.
There are also a number of spectroscope enclosures on thingiverse, but it's always so hard to gauge if any of the projects are actually worth printing. The most dead-simple and cheap example I found used the same slit/CD plastic combo capped onto the ends of a paper towel tube.
Generally, Public Lab builds and 3d print plans are worth your time. Everything they list is well-considered and well-maintained. When the stodgy old magazine The Economist wrote a "Punk Science" article about DIY science, they actually got them include a cut-out page to build a spectrometer :)
https://publiclab.org/wiki/economist