Short answer to your question, I use the Titmus II. It's old, but it does the job.
I would email Nancy Katz email@example.com and see what she suggests. Or you can call the office (708) 544-5300.
You may need to borrow someone's equipment to go through the certification processes, but you'll need your own equipment to be able to screen kiddos once you are certified. Once you submit your application and your date is approved by IDPH, you'll get more information than you'll ever want to know.
Also, what about hearing? Do you have a machine for that? You'll need to do both hearing and vision certification at the same time.