I have a Selle An-Atomica on my main road bike which has Brooks-style bag loops on it.

Currently I am using a "Transit Wedge 125" from Performance (the capacity is supposedly 125 cubic inches when fully expanded). It holds what I want but doesn't mesh well with my seat post & the long rails on the An-Atomica. The loop which goes around the seat post slips upward, so the back of the bag drops down toward my rear tire. It's annoying. It doesn't matter how tight I make it, it will slip down. I put a bit of duct tape around my seat post for a while, but that wasn't a good solution.

So I was wondering... aren't there any inexpensive, cordura or equivalent, zipper-closed bags out there which can be attached via Brooks-style bag loops? I've looked at Rivbikes, et al., and what I've seen so far is either 1) very pricey, 2) too elegant, 3) a style which I don't want, or some/all of the above. The ideal bag would attach via the Brooks-style loops plus a strap around the seatpost. I'd like reasonable capacity, too... 125 cubic inches is not bad. I don't care if it borders on fredliness, because I want it to work well.

If necessary, I'll sew something onto my current bag. But it has some kind of plastic on the top, under the nylon, so it won't be easy. I figured to ask here before I start sewing, or whatever.

The one Acorn bag seemed reasonable, apart from the price. My wife would explode if she knew I spent $89 or more on a seat bag.