i used both the marena one you listed and this one from amazon XUJI Women Tomboy Elastic Band... https://www.amazon.com/dp/B07W56CGBS?ref=ppx_pop_mob_ap_share both were recommended by my surgeon. i actually liked the amazon one better since it had 3 different tightness settings, but it did lose its elasticity over time so i had to tighten it. if you can afford it is recommend 2 binders so you can wear one while the other is washed.
to get the size i measured the widest part of my ribs, which for me was essentially where a bra band would sit.
my surgeon recommended this one https://www.amazon.com/dp/B07W56CGBS?ref=ppx_pop_mob_ap_share
my surgeon recommended this one XUJI Women Tomboy Elastic Band... https://www.amazon.com/dp/B07W56CGBS?ref=ppx_pop_mob_ap_share
i had to buy it and some supplies for medical dressing based on an amazon wish list they sent me. my surgeon recommended this one https://www.amazon.com/dp/B07W56CGBS?ref=ppx_pop_mob_ap_share so it was pretty affordable