The Burgess Dwarf Hamster Harvest has a lot of canary seed and grass pellets in it which I have found that nearly all of mine will leave however May likes the sunflower hearts and mealworms in it and it's one you could use as a base or alternate with other foods. I'll normally give May some of the Supreme Science Selective Biscuits a couple of times a week and she's usually happy enough to eat it. Being a complete food, it's a way of ensuring a fussy eater is getting all the nutrients that they need.
If you're in the UK or the Netherlands and you sign up for the Happy Hoppers club with Supreme Petfoods they'll send you a £2 off voucher that you can use on their food, treats or toys providing you use it with a member retailer. There is a list on their site of these so it's worth a look to see if there's one near you.
Here's their site:
Supreme Pet Foods | Selective Pet Foods Range
Here's the form to join the Happy Hoppers Club:
Happy Hoppers Club | Supreme Petfoods