I don't know the best place to post this, but is there some way of "plugging in" an electronic device which accepts AAA batteries, but doesn't have an AC adapter power jack (without opening up / soldering)?
That is, there are AC adapters which have 9V battery plugs, but I've never seen anything which fits into AAA (or AA) battery compartments (which I don't get, since the batteries are a standard size).
Hey, Danr, what I've done in the past is just find the right power supply for the device and then "southern-engineer" an adapter. I've done an old "boom box" in the '80's when they were called that. It required 8 D-cell batteries which is 1.5 volts x 8 = 12 volts and since I wanted to run it in the car (I was a kid and I wanted to listen to my stuff while my parents drove Florida) I cut a wood dowel rod and ran one wire to a screw at the end of one rod and one wire to a screw at the end of the the other rod. Then I cut the two dowel rods (so they would fit in sorta like batteries (one goes in and hits the positive lead, one goes in an compresses the spring at the negative end), and put them in (each dowel rod was roughly the length of four D-cell batteries) cut in half to make four pieces of wood, two with screws in the end with wires attached, so the rods filled in the space of the batteries. Then I ran the wires to a cig lighter adapter. Done!
Much more recently I did a similar mod for a Creative Labs Zen Nano Plus 1 GB. It runs on one 1.5 volt AAA battery but I was using it in my shop to provide audio source to my big stereo out there. I hated having to feed it AAA batteries so frequently and I had a surplus of D-cell batteries so a mod was in order. I took a Bic Round Stic pen (I love those pens, it was a sacrifice) and cut it down to length to fit in the AAA socket/pocket of the Zen. I then put some phone wire (solid core, thin (maybe 24 ga?)) wire between then tip and the butt and ran them to a D-cell battery. It worked. The pen held the wires against the contacts and viola! Power! The D-cell ran for weeks at my usage rates instead of days.
All that said, basically, what you need is a way to "southern- engineer" your device. There is not, that I know of, a commercial way to connect a power supply into the battery cavity of a device. What you can do, though, is simply find the right power supply and then find a way to lodge the conductors against the pickups in the device (be careful of polarity (make sure you get + to + and - to -). You could just try pinching the wires from your alternative source into the springs/coils pickups of the device (I did) but it doesn't seem to work so well (my attempts SUCKED; kept breaking contact intermittently).
Hope this helps you. When you find a solution that works for you, please post back to let us know and help us all.
This is exactly what I did for my sons Sandisk player to use a larger longer lasting battery. Cut a 3/8-inch dowel rod to length, apply copper foil to both ends and a 4-40 screw to the '+' end. solder twisted pair somewhere along the sides and run it to the larger cell contained in a belt holder. Worked like a charm and I didn't have to buy a gazillion AAA cells! File a small notch into the battery door where the wires come out. good luck.