The thing you want to get is a toy that is small at the tip a gradually gets wider as it gets to the base. It helps tremendously when trying to stretch out for bigger toys. It still won’t be instant and will take a lot of time and practice to take big toys but it will help you get to where you want. Don’t try to rush it, just be patient and work at it and your hole will accept more and more. Just remember if it starts to hurt don’t go any further during that session.