Any recommendations on light tight material for intake hole

My grow cupboard has 1 silly yet major flaw... Here we go:

At the bottom of my grow cupboard are two round air-intake holes (allows air to be sucked in because the exhaust fan creates a vacume within the cupboard) which Ive covered with fly mesh to prevent dust & debris from being sucked in. However because it is mesh it is not light tight (a big issue during the night cycle), I dont think I can cover it with a thicker fabric as it stops air flow (suction).

Does anyone feel my pain?

Any recommendations...?

Anyone...?

Find a few pvc pipe 90's, 2-3 turns and no light......or dryer vent hose, few turns and waa laa!

Dryer hose THC? Go right now to your HID and look through the hose, the aluminum hoses are so transparent I switched to insulated.

I found black nylons (steal them from her) are the best for light blockage through tubes, really darkens it out.

triple thick

Filters the air too