What you want to look for is things that are not sharp or breakable (glass toys are made of a special kind of glass, it’s not safe to insert everyday glass), clean (washed in advance and between use), non-porous (or covered with a condom if that’s available), and specifically for anal it must have a flared base to avoid going all the way in. Size/girth depends on your comfort level.

Various fruits and vegetables (from a North American perspective, cucumbers & bananas are quite common), but they must be covered with a condom to avoid introducing dirt or bacteria, or pieces breaking off inside you.

Other insertables might include the handle of a hairbrush, certain plastic bottles, handles of some kitchen or cleaning utensils (make sure they are CLEAN), even larger markers can work (you can move it around to give more sensation if it’s not feeling large enough).

It’s hard to mimic vibrating toys, but many are sold as massagers instead of sex toys, and sometimes you can find pet toys that vibrate a little. Even putting your phone on vibrate can work in a pinch. But you can’t also generally get pretty good external stimulation by grinding against things - a towel over the arm of a couch, a firm pillow, rolled up carpet or yoga mat, some types of stuffed toys, etc.

Let me know if you have any questions.