A bath bench, that extends over the side of the tub, is a good option, especially if you have lower limb weakness. It may not work if your tub/shower is enclosed by a sliding glass door. However, there are several shower chairs and benches to choose from. You might want to shop around for the best price.
I have seen some people use a light weight plastic chair, but I consider them too unsafe, because they are unstable.
No matter what type of chair, it is important that you have grab bars, securely installed in the shower/tub and by the toilet. Also, an elevated (riser) seat for the toilet will help keep you safe.
Usually someone who has had a hip replacement is eligible for a few home health visits by a therapist, who can evaluate the equipment and make suggestions for adaptations to keep you safe The therapist will also help you learn how to get in and out of the shower/tub without hurting yourself. Even if you received inpatient therapy after surgery, I always recommend a Home Health visit by a therapist. They can adapt their teaching based on the actual home situation.