This is a list of miniature spectrometers offered.
Scientific article
Portable Spectroscopy. Includes a review of SCiO (not impressining)
Real miniature spectrometers
Hamamatsu C12880MA
This sensor is directly useful with Arduino, and included as a sensor and a module.
In the pipeline
Crowdfunding etc
[Kris Winer] aims to make this happen with the Compact, $25 Spectrometer entry for The 2018 Hackaday Prize. The project takes advantage of smaller and smarter spectral sensors to fit the essential bits onto a PCB that’s less than an inch square. If the sensors do the job as expected then that’s a big part of the functionality of a reflectance spectrometer contained in a PCB less than an inch square and under $25; definitely a feat we’re happy to see.
Papp, Donald, 20190525 TINY $25 SPECTROMETER AIMS TO IDENTIFY MATERIALS WITH EASE
(Designing and building an inexpensive spectrometer just got easier with AMS’ new 3-chip AS7265X smart spectral sensor; once this is working, building a modern tricorder should be a piece of cake!)[https://hackaday.io/project/143014-compact-25-spectrometer]
REALLY EXCITING, at 50 USD and 20 nm spectral resolution. Now for sale on Tindie!
SCiO
700-1100 nm, 12 bands. And you can not get any spectra, only via online connection.
SCiO handheld consumer spectrometer
Comment found: Please be careful and heed the lessons from the SCiO hype and subsequent fiasco
Lightmachnery.com
Lightmachnery.com does not seem to offer consumer market spectrometers.
oceanoptics.com
Oceanoptics.com always comes out in all google searches. I do not find any consumer products.
Stellarnet.us
Stellarnet.us also always come out. They have a series called:
BLUE-Wave Miniature Spectrometer
https://www.stellarnet.us/spectrometers/blue-wave-miniature-spectrometers/ But it is not really a spectrometer that you carry around and attach to your phone.
Green-Wave Miniature Spectrometer
https://www.stellarnet.us/spectrometers/green-wave-low-cost-spectrometers/ But it is not really a spectrometer that you carry around and attach to your phone.