Shure SE215’s with triple-flange eartips. They block lots of background noise, and they will fit even small ear canals, they are the only sort that I can wear that let the ‘phones seal properly, all other buds just don’t fit, and I’ve tried all sizes. Your best bet is to get the SE215’s, which really are fantastic ‘phones, and then splash some cash, maybe ask for Christmas money towards them, and get some proper custom-fit silicon eartips for them, you’ll then have proper in-ear monitors that will fit you perfectly. Not cheap, around £112 now, but really worth doing, especially with the Shure’s, which sound marvellous.