"Have charge of" is a commonly used phrase to describe the responsibility of taking care of something or someone. However, there are many other synonyms that can be used to convey the same meaning. For instance, "be responsible for," "supervise," "oversee," "manage," and "direct" are all excellent alternatives. Additionally, you could use "control," "govern," "command," or "guide." The choice of synonym depends on the specific context and tone of the message being conveyed. Nonetheless, using synonyms for "have charge of" is a great way to vary one's vocabulary and keep writing fresh and interesting.