In Nature Calling, I talked about replacing your low toilet with one that is higher.
This is not always possible or feasible, so you may need to buy an elevated toilet seat. They come in a variety of styles with a range of features, including locks so that they don't slip and handles to aid you in standing. The types of materials used vary, as well. I'm sorry that I can't give you specific advice on this, since I bought mine over fifteen years ago.
Before you make this purchase, ask for recommendations. They are not created equal, nor are they equal in terms of ease of cleaning. By far, the easiest to clean is the in-house toilet seat.