I have not been able to find any information that indicates that there are seedless varieties of sunflowers on the market. There are pollenless sunflowers, but they are still capable of producing seeds. If you are only growing pollenless varieties, it is less likely that you will get seeds. (If a bee flies from a sunflower in a neighbor's yard that has pollen, it can accidentally pollenate your sunflowers, resulting in seeds. The further away sunflowers with pollen are, the less likely a bee will transfer it to your plants.)

Search online for "pollenless" sunflowers. You might also look for "florist" sunflowers. Read the descriptions closely to make sure they are pollen-free. 

However, if you are trying to avoid seeds for the reason that they attract squirrels or come up in your flower beds, you can easily solve that problem by cutting the flowers. Cut flowers will not produce seeds. You can either cut them right before the blooms fully open for bouquets or wait until the flower is declining, cut it off (aka deadhead it), and throw it in the compost.