Thank you for the recommendation, @miwojc. I am using Google Collab, so this prompted me to look up the installation guide for that IDE. This notebook provided a solution:
import sys
if 'google.colab' in sys.modules:
!pip install -q dtreeviz
import sys
import os
# add library module to PYTHONPATH
sys.path.append(f"{os.getcwd()}/../")
from sklearn.datasets import *
from dtreeviz.trees import *
from IPython.display import Image, display_svg, SVG