Well, I love my 'rat. Never leave home without it, and I'm tempted to get it a mate. That being said, there alternatives....
Outdoor Reasearch used to make what they called the Outdoor Organizer, and the smaller two were the size of a Park-Rat.
Blackhawk makes a clone of the 'rat without the lining, but from the pictures I've seen, it looks to be identical. OD on OD is kinda hard to tell. It is a little less expensive, but that's what happens when the label doesn't say made in the USA.
If you want small, there are a lot of people with smaller organizers. SpecOps makes one, with Blackhawk making a knock off. CountyComm has the knock off for like ten bucks. I've looked at the CC item, and it's not at all bad.
If you know how to sew, or know someone who does who you can bribe, you can get exactly what you think you need made.
That being said, I don't think you can beat the SOB Pack-Rat. Mine is stuffed full with a mix of school, survival, medical and technical stuff. In the past three months it has been dragged, sat on, tossed, dropped, skidded across the floor, and definantly over stuffed, and it doesn't show signs of wanting anything but more.
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-IronRaven
When a man dare not speak without malice for fear of giving insult, that is when truth starts to die. Truth is the truest freedom.