Very simple filament sensor mount, designed for ShadowHawk69's Shadowmega generic carriage (massive modification of M3D's ProMega).
The filament sensor used here is: https://www.amazon.com/dp/B07JJ2835X?ref_=ppx_hzsearch_conn_dt_b_fed_asin_title_4.
A similar one, unverified, is https://www.amazon.com/Diitao-Filament-Detection-Accessories-Transparent/dp/B0CQP94MZ6?th=1

It's inside the chamber, it should be made of PETG or higher (PC, Nylon, etc.).