First, check about the strawberries, I remember being told to wait until at least one before feeding babies strawberries...Snack ideas - some may be better for on the go, others for highchair, Also, some may be too hard - don't know how your son chews and how many teeth he has...but here are some ideas...
Fruit (you said you barely give him any, but cut up blueberries are great, banana, avocado, peaches...)
Several companies make puff snacks that more or less dissolve in your mouth.
Cheese cut small.
At his age, he probably doesn't need real snacks during the day - most foods are pretty new...we also like soy yogurt, tofu, and teething crackers.