2 Sets Adjustable Jeans Button Pant Waist Tightener, Detachable Decorative Waist Buckle, No Sew and No Tools Button Pins for Jeans.

with pull on bottoms or more casual slacks that I don't want to take to a tailor, I use waist clips in the waist band portion above my butt. not this exact pair but for ideas: https://www.amazon.com/dp/B09Y1HTCJ6?th=1