This is a remix from humebeam's design. Thanks humebeam. As the silica gel will only be poured once, I make the hole self-tap with a M3 x 20mm screw to save an insert.

https://www.amazon.ca/dp/B0BXJNJ73M?ref=ppx_yo2ov_dt_b_product_details&th=1

This is the silica bead I used. It should be available in any Amazon store. The beads I used are 3-5mm in diameter as specified. Any silica gel with this diameter range or bigger would work. I sill don't know if the head of the bolt would catch spark when I microwave it after the beads are saturated. I will keep you updated. 

(Update Mar 11, 2024: I microwaved the setting. It didn't catch any spark. At least for my screw and microwave, which is a very typical Hamilton microwave from Walmart Canada. Thanks AyAyRon remind me of the update)