Suggest a cheap portable mono amp design for a friend? SOLVED

I need to make the cheapest mono amp that I can. It's for a friend who is hard of hearing. It will be used to amplify a race scanner, and headset. The headset is over the ear, sound isolating and monaural. I'm happy to de-solder and recycle components if I can find them. I would love to get 4-5 hours of battery life, but that's not strictly necessary. I don't think it needs a volume knob, because there is one on the scanner, but you guys probably know better than me. Any help would be greatly appreciated. Thanks in advance.

Thanks guys.    Any guess on battery life with the opa132 or the opa690?

Nice. Thanks. I should have read further down for that.

Hi, again. So I found an opamp inside some other gear that I intend to desolder and use for this project if you guys think it will be acceptable. The opamp is BA4560. I found the datasheet here, but I don't know what to look for for comparison to the OPA134, nor how to correct for any differences. Again sound quality is of very little concern for this project. Small price and big volume are the only real concerns. Also if the BA4560 is acceptable, should I be concerned with figure 9? If so, could you tell me if I'm correct in my understanding that Vcc is the +4.5V lead, Vee is the -4.5V lead, and Vicm is for the input from the scanner? I'm a bit of an electronics noob here, so please forgive any stupid questions.

So I settled on a plain old Cmoy with a power/volume knob that I cannibalized from a discarded set of pc speakers. I was a bit concerned about using a mosfet design, because he'll probably have it in his pocket, and I have no idea how much that will heat up. I modified Chu Moy's drawings so that I could understand them easier in the workshop. Here's what I did.

I used a Sucrets tin because its just slightly taller than an altoids tin, and you can stand a 9V on edge in one. Since this was my first amp, I thought the extra space might be important.

I like the Idea of a volume knob, but I don't like how they stick out. They always look like they are going to break off. The guy I built it for already has volume knobs on his scanner and his headphones, so he won't need to get adjust volume at the amp more than once each use. I figured the best compromise was to keep it inside the box.

Like I said the knob has an integrated power switch so power can be fully shut off. He's a bit of a redneck so he was thrilled about the (LED) light too.

I salvaged some bent pins out of some other disassembled junk that I had lying around and used them to make the battery compartment. The board is held in place with double stick foam.

The board is from radio shack. It has copper rings on each hole, and cost me $2. All of the other components were bought on digi-key for less than $10 after shipping. I charged him $12 for the project and thanked him for the excuse to play with some fun stuff. I know that the layout is sub optimal, but I just laid it out as I went along. I have no idea how to properly design a board, so I'll have to be content with this one for now. It works great for him. I wound up using the opa-134pa for simplicity. ie. I didn't have to put any thought into that part of things. The finished amp has plenty of amplification with no distortion, and the battery lasted about a week for me while I tested it out, before giving it to him. I didn't have it plugged into anything most of the time (only about 8 hours), but I never turned it off that week. I used it to boost my kids mp3 players going into my fm transmitter, and it cleared the signal right up, as well as using it as a pre-amp to feed the same mp3 player to a pair of computer speakers. I also tried it out with my iAudio7 to see how loud it would go with my phillips ear buds. That was stupid though. It actually physically hurt. The only negative thing is that there is a constant minor hiss. It isn't loud enough for my friend to hear, but like I said, he's a little deaf. Thanks for the input guys. it helped.

P.S. Sorry for the crappy cell phone pics. It's all I've got right now.

EDIT: I'm not sorry yet though... I'm new still so my post is being approved first. Then I'll be sorry.