Best I can do is give you a
Google search and suggest you start interviewing the practices close to you that don't have horrible reviews noted.
You'll want a vet who:
1) supports home testing of blood glucose and is OK about using a human glucometer
2) supports feeding a low carbohydrate over the counter cat food, or raw low carb food
3) is either up to date, or willing to do the homework to become up to date on feline diabetes and common comorbidities.
4) if up to date, is familiar with the use of ProZinc, PZI, Lantus, and/or Levemir
IN CATS; ask how they determine initial dosing and how often the dose is given (should either be based on body weight or starting low at 0.5 units and dosing should be twice a day)
5) has pricing you can live with - check office visit fee, vaccine fee, CBC and chemistry fee, etc. Ask how often they have you bring the diabetic cat in and for what reasons (if you are home testing, you can do curves and averages at home, and the cat doesn't get 'regulated' at the vet office where stress makes the numbers unreliable)
6) if currently treating diabetic cats, ask how long they usually survive (should be several years)