I bought this from Walmart. It comes with stainless steel springs made specifically for fermenting. I haven't used it yet, but reviews say they work well.

Try these. Auto-burping, no flys. I love mine. No papertowels over and over.

IF the starter does escape it can through the tiny holes in the top.

A bit more expensive on Amazon (cheap at target but assuming you aren’t US).

Ball Fermentation Lids and Springs, 32oz, Metal https://www.amazon.com/dp/B084CZ7FHM/ref=cm_sw_r_cp_api_glt_fabc_H6VJRB1HGM2FCKK1M0E3

They just screw onto any standard wide mouth jar.