You shouldn't read anything on this page or do anything with the information I've come across. I have, and it's worked for me, but it might make your pretty cell phone explode in your face or catch on fire or who knows what other bad things. Some of this is based on assumptions and trial and error, not out of inside information, so don't rely on it or anything.
So, while I won't give you step by step instructions, the following information should give you what you need to make something if you have some electronics skills and some spare parts lying around like I did. The important part of course is the SCH-a310 pinout you need to be able to connect a charger to the phone.
If you look at the bottom of your phone you'll see a connector with 18 pins. Each pin is double sided, so top and bottom are the same connection. The pin on the far left, with the keypad facing up, is pin number 1. The far right is 18. We'll need four of these pins. First, to convince your phone that there's a charger plugged in, you need to connect pins 3 and 4 together. If you do this, and your battery isn't completely dead, the phone will claim it's charging even though it's not actually. You must also apply 5 volts to supply the actual power for charging. To do that, pin 15 is the ground connection and pin 18 is the 5 volt connection. You should probably fuse or provide diode protection or other nice safety measures to these connections. I leave that up to you. I'm also suspicious that pin 16 is also a ground connection and pin 17 is also a 5 volt connection so that the pins can divide the high current levels, but I haven't verified that.
So when I had the phone battery pretty well discharged and off, I tried charging things up. The phone drew almost 1 amp of current as it began charging. Even when it's pretty well charged up the phone still draws half an ampere. It'd probably try to take more if it were charging while it was on or making a phone call. So be careful to make sure the wires you use are all the right size. The phone might even want to use a second pin somewhere on the charger, I don't really know. I got it working without any fires so far, but I let it charge up a ways before I go using the phone to make a phone call.