Hey, the grippys are amazing, we used these but there are lots of different styles that work well.
This is a gentle suggestion, but have you considered an occupational therapy evaluation? My oldest hated coloring until he started working with an OT at 4 years old for other things and it meant getting better hand/grip strength and seriously improved fine dexterity. He's 7 now and thriving, just needed some help.
That's quite a contortion! But it's never too late to train yourself to grip properly. It's a long term investment that will be painful now but will help you in school and the rest of your life. They even have gadgets to help: https://www.amazon.com/DMFLY-Handwriting-Correction-Preschoolers-Ventilation/dp/B07PDKJQX1