Try Spinfit CP100+, W1, CP145, etc. Those have a rotation gimmick that actually kinda works.

For the CP100+ and W1, those also have medical grade silicone material that should help with the itching/uncomfortableness/allergies/etc. A lot of new silicone ear tips these days basically have that medical grade silicone material now, but in the future, always make sure to get that so that your ears don't itch/etc.

Yes, you can use different-sized ear tips to have a better fit/seal, but for me the sound can change drastically as the bass/treble/etc. shift to one side and so on due to the mismatched dimensions/sizing/etc. of the ear tips.

Try Spinfit W1, FiiO HS18, AZLA SednaEarfit XELASTEC, Dunu S&S, etc. ear tips for possibly better fit/seal, noise reduction/isolation, and comfort.

The dimensions/sizing/measurements/etc. for most ear tips these days will be on Amazon/AliExpress/HiFiGo/etc. Unfortunately you have to blind buy the ear tips in order to get a feel for the dimensions/measurement/etc. that you like for your ears. Remember, this will also change with different IEMs as they'll have different nozzle length, nozzle angle, and so on.

For Spinfits, usually some AliExpress storefronts or like say MTMTaudio/etc. will allow people to only get 2 pieces of 1 size for cheaper or half price of the usual price. Like some Spinfits models are often $10 with 4 pieces of 1 size and so they sell it for $5 for 2 pieces.

Cheap ear tips (basically FiiO HS18, Spinfit from some AliExpress storefronts, Chinese websites like MTMTaudio/et cetera, and so on) and possibly better soundstage: https://www.reddit.com/r/HeadphoneAdvice/comments/1157giz/upgrade_imaging_with_balanced_cable_iem_or/j90a003/

Same info about different ear canals size: https://www.reddit.com/r/headphones/comments/11a5sle/any_tips_to_make_my_moondrop_katos_not_fall_out/j9r2tjz/