I am trying to find the best way to state the following.
- You may need to request this information with your optometrist.
- You may need to request this information at your optometrist.
- Something else entirely.
Can anyone help me out?
"Request with" is not used.
Usually, you would request information from your optometrist, especially if you will ask it of your optometrist directly.
"Request this information at your optometrist" may be used in the case where you would ask for at your optometrist's office, but not necessarily ask your optometrist. You may ask the receptionist for such information.
There is also the use "request of", which generally means you are asking someone for something more tangible than information, or asking them to do something for you.
If you take a look at the following:
You see that "request with" and "request at" have minimal uses, and if you look at some of the samples, you can see that they are not used with your intended meaning.
I would say "You may need to request this information from your optometrist."
In general communication, both of your examples would suffice, and would usually not be mistaken to mean something else, but taken literally:
As Jim said, of would indicate that you wanted the optometrist to do the information.