A good one to try is Dr. Dog Natural Bug n' Out. It is a blend of citronella, eucalyptus, tea tree and other oils. It repels fleas, flies, mosquitoes, chiggers, ticks, gnats, and lice, and there is a money-back guarantee if you're not completely satisfied (but you will be!) You can go to www.doctordog.com, or call 1-800-PETS-NOW.
I really like the Flea Flicker from Aromadog - I sell the line here and had never tried it until my Mosquito trap died and there are clouds of mosquitos here so I tried it and it is wonderful - all organic ingredients safe for all dogs and humans. I have ordered a new mosquito trap - cannot live without it here.
When the trap is running I have NO mosquitos on the property - amazing