It's not much help, but the best I've seen are $8.00 a box (25) steel #1 loads at a local Dick's Sporting Goods. I got a few boxes for a friend to try because he wanted something cheap in a 2-3/4" shell and it was on sale. The regular price was $9.99. It worked well for him, but isn't waterproof. I want to say it was Remington, but really don't remember. It was obviously a promo load. Dick's has a web site but they don't sell ammo online.
Otherwise, in my experience, it's usually just a matter of finding discontinued/last year's ammo on sale and taking what they have left.
I thought about Cabela's, but they never list any 2-3/4" steel IIRC. May be worth a phone call to see. A year or so ago they were selling Remington Nitro-Steel 3" loads for around $10/box plus shipping, or 10 boxes for $90 plus about $9 shipping - a heck of lot cheaper than the local shops that seem to run $15-$20/box.
John
