Just got a few of these interesting dry fire training aids. These work by using a spring and detent to press your trigger forward on 9mm and .40 double stack Glock models, emulating trigger reset. Comes with spare springs of varying weight to better replicate your trigger.

https://www.westernmetal.ca/product/ttrigger-mag-glock-red-a-ttr-tt-mg-g-09-rd/
Take a look!

https://www.westernmetal.ca/product/ttrigger-mag-glock-red-a-ttr-tt-mg-g-09-rd/
Take a look!