Finding one that would be suitable to automatically feed them for 2 weeks or longer is quite difficult. The most I have seen them for if I am honest is for about 6 - 7 days and then they would need to be refilled.
This one I found feeds for up to 6 days
Eheim Everyday Fish Feeder Programmable Automatic0;Food Dispenser : Amazon.co.uk: Pet Supplies
Another alternative would be to maybe ask a family member or a friend to come round and maybe fill the automatic feeder after 6 days when it would be empty so it could last longer if you are away for two weeks or over?