Part of the reason your TSC may not carry it is due to purchase/sell. If it doesn't get purchased, they can't justify bringing it in. Big $$ loss for them if they can't sell it in a timely manner. Our TSC has some feeds they don't bring in. Others they do, but they don't sell regularly, so the bags are older and sometimes I've found some feeds to be not that good and/or out of date/OLD (after getting several bad bags of Mini horse & pony feed that our 30 head of ponies refused to eat, I quit trying. I buy more local now, if I can). Our local TSC doesn't carry some chicken feeds because another feed store less than 2 miles away carries them. BUT they do have different ones that the other feed store does not... Yes, the store managers check each others' stores out, LOL. Good business sense.
You can see if there is another TSC in your state that will do an "in-store" transfer. That means that another store has it, and they can ship it to your store. When shipping it, the shipping charges are covered by the TSC's involved. THEN, if you are able to drum up any one else that can purchase that same feed, they (your TSC) will look at bringing it in on a regular basis. I have not done "in-store" transfers for feed, but I have for 8' steel posts. Used to be able to get them at any TSC, but not anymore. I can have them shipped from Greensboro to Sanford and not make the drive myself to Greensboro. It's my understanding that they can do an "in-store" transfer from any store in NC and in some cases, from out of state. EDIT TO ADD - I had to do the "foot work" to find the 8' posts that I used to purchase all the time. The new employees at the Sanford TSC (rebuilt 2 yrs after the tornado wiped the original out in 2011) are younger and didn't know that the posts that don't show on their available inventory ARE still carried by some TSC's. I worked hard to get those in-store transfers - sometimes it is easier to drive to another town (and more fun, but have to plan the day as it is a LONG one in a major city on both ends of heavy traffic - AM & PM).
As to comparing feeds, you don't even need the feed tag. Purina feeds are online and
Omelene 200 has it's own PDF that anyone can print out or copy. You then can carry that with you. If you have a phone that takes pics, don't even need to print it out!
If you are in a really rural area, you might consider giving your business to a local feed mill. They will have some horse feeds that are standard and they can possibly mix feed for you (depends on the mill). Have you checked to see who else may carry Purina feeds? Over the last 20 years, we've had several feed stores go out of business, but others have picked up the slack and carried what the ones closing may have been carrying. We even had 1 town about 50 miles away from me now (was 25 before we moved) close a MAJOR distributor of Purina feeds about 9 yrs ago. No one picked up that Purina dealership again, but other stores started carrying more Purina feeds... When I'm talking "local", I'm talking about many different small towns that may carry feeds. I wasn't unusual for us to go to different towns to get different products. Some of those towns were just a few miles apart on the same highways, some were much further (50-100+). When we lived in MT from 95-97, we bought feed locally at the feed mill in Shelby (9 miles from our house), "locally" from Cut Bank (32 miles from our house on the same highway as Shelby) and from 3 different "big box stores" in Great Falls (96 miles from our house). I don't know which stores in MT are still in existence, but do know that some that I have purchased from here in NC are no longer in business.