Yup, DuMor is nothing but 100% packaged by Purina to be sold at TSC as its "house brand". Nothing special, nothing horrid. Just is what it is. Frankly, the price is not reduced enough for being generic, imho. If it were $2 cheaper a 50#, it would be much better. Oh well.
if you google feed store or feed and seed you will likely get some hits of what is in your area. Different areas of the country have different "country stores" like Tractor Supply, Atwoods, Farm and Fleet, etc, etc. Those are chain stores and they typically have something they have sacked up just for them. Some will have Purina. Some will have Kent Feeds, another well known brand.
If you give us an idea where you located, we could probably point you in the right direction.
We like the DuMor Layer Crumbles and have recently switched to layer pellets (less waste). The Chick Starter seems pretty good, in my humble opinion much better than the locally made starter mash which tends to create a huge mess and alot of waste. We especially like that the DuMor brand products we use do not contain animal products. Good luck.