Found the website and schematic that I first found when looking to build battery powered CBG amps. But the schematic I used was a little different. I will get the hand drawn copy from my shop, make a clean copy and post it later. You can also find some proven circuits at runoffgroove.com
Look for the Ruby amp or the Little Gem. Relatively simple and inexpensive to build.
Yes, I have a schematic...found it on web search...under "battery powered guitar amp schematics".
It uses a LM386-N1 ic chip, a 2"x2" board, a 10uF 16 volt capacitor (radial), a 220uF cap w/ same values, a 1K ohm ceramic disc capacitor, and if you want an LED power-on indicator light, it uses a 330 ohm 1/4 watt carbon resistor. Volume Potentiometer is a 10K ohm, and a basic on-off toggle switch and a 9 volt battery clip.
You can add a wall-wart (ac adapter) component to save battery power, but that requires adding a JFET transistor, which are tricky to solder in with out a good heat sink...the JFET will self-destruct if too hot and a static discharge can do same damage.
I'll look for copy of schamatic and see if I can dwonload it to clubhouse.