Poor man's 50$ cryostat for photoluminescence measurements

About this project:
https://www.researchgate.net/project/Poor-mans-50-cryostat-for-PL-measurements

Cheap cooling system to substitute Fluorolog custom LN2 cryostat for PL measurements

What to buy:

1. Dewar flask, clear http://www.leybold-shop.com/chemistry/product-catalogue-chemistry-biology/natural-sciences-student-experiments/inorganic-organic-chemistry/inorganic-chemistry/dewar-flask-clear-for-demonstration-38640.html (approx. 40$)
   2 . Chemical vial (approx. 2$)

IMPORTANT SAFETY NOTE: in order to prevent liquid oxygen condensation, the vial should be filled with N2 gas and tightly closed.