Is he struggling with fine motor b/c of strength or b/c of dexterity? Are you worried about his knowledge of letter/number identification or is it that you are worried about Handwriting? If you have enough concerns to want to get him into an OT you can locate one through a clinical setting. My son saw a clinical OT for 4 years which was referred to with a script from the doctor. Insurance paid for it, but of course that would depend on your insurance etc.
If he did not qualify for services then it must be a slight problem to keep an eye on, but not anything to get overly worked up about. When my son attended Kindergarten his past year I was a nervous wreck and convinced he was not ready. Over the year in Kindergarten he has absolutely blossomed into a new kid! I am so proud of him.
As far as if you concerned about his fine motor, it's always good to do exercises that will build his web space (the area between the first 2 fingers and the thumb). The web space muscles are the ones utilized for activities such as holding a pencil. You can exercise his web space with activities that require squeezing such as squirting a squirt bottle, a garlic press with play dough in it, etc. One activity I did with my son was we would write on a mirror with shaving cream and our fingers. We would write shapes, the alphabet, numbers etc. Then we would use the squirt bottle to rinse it and do it again. It practiced those skills, built web space, and it was fun!
There is also an awesome program called Handwriting Without Tears that was created by an OT after she saw her own child struggle with handwriting. It is AWESOME and I used it with my son. http://www.hwtears.com/hwt
Good luck! Your son is so lucky to have a mommy who wants to give him an extra start in his education!!!