Safe mixes:
No1 - For Female and Young Rats - £0.72 : ratRations.com
No2 - Suitable For All Rats - £0.78 : ratRations.com
No3 - with Soya - Geriatric and Kidney Support Plus - £1.20 : ratRations.com
No5 - Mums and Babies Basic - £0.66 : ratRations.com
No6 - Geriatric and Kidney Support - £0.90 : ratRations.com
http://www.ratrations.com/seed-mixture-p-418.html
The last mix is in some of the other foods,so it could be bought on its own or already in another mix.You can feed seeds by hand just as you could for hamsters,which is an excellent treat without having to use sugary storebought treats as you probably already know
Treats really depend on which mix you choose,since you can add extra seeds of different types or a variety of safe nuts.In general the same nuts that are hamster safe are also rat safe.Just avoid unnecessary added sugars,artificial preservatives(BHA/BHT/ethoxyquin,unspecified antioxidants and such which are likely BHA/BHT/ethoxyquin,and sulfur dioxide are most common),and pretty much unsafe foods would be mostly the same as hamsters!