Hmm... so all my phone adapters are USB wall adapters.
How much does voltage matter here? The toy does have a pretty reasonable tolerance and range I'm guessing, and also has two speed setting already available.
Could I use a 6V 500ma AC adapter? Like this one:http://www.ebay.com/itm/6V-500mA-AC-Adapter-Battery-Charger-w-Alligator-Clips-/200600186004 Then I could just clip the AC adapters straight on and not have to worry about stripping or soldering.
Alternatively, could I just get this AC barrel connector to alligator clip connector and clip it onto whatever available AC adapter I can find?
Rethinking things, if the toy is already wired up with a speed regulator and not knowing the quality or rating of cheap Chinese components that were thrown into the mix or the wiring schematics, I can only err on the side of caution with my advice at this point and assume that the device is designed to expect and operate on 4.5V 1000mA only (4.5W output), assuming the batteries are wired in series. +/-15% of expected tolerance is usually fine in these sorts of situations unless you're dealing with delicate electronics (which you aren't). Theoretically, you'd probably be fine (if not a bit underpowered - 6V*0.5A=3W output) with that, but underpowering some motors can also be problematic, so your fast setting would probably become slow and your slow a cranky motor.
By the way, for anyone interested... it's easy to work out voltage and amperage requirements of battery devices for these sorts of projects. General rule of thumb on average specs for AAA through D cells is 1.5V 1000mA per. If they're wired in series (end to end), multiply the voltage by the number of cells. If wired in parallel (side by side matching polarity), multiply the amperage by the number of cells. A count of four AA batteries can yield one of three power configurations - series: 6V 1000mA, parallel: 1.5V 4000mA, parallel+series: 3V 2000mA. Three AA cells will only provide one of the two following power configurations - series: 4.5V 1000mA, parallel: 1.5V 3000mA. Details with diagrams
here. It's important to know how the batteries are wired when you make these calculations with most things, though with motor use, they'll all provide the same wattage.
I don't know anything about this toy, and I hate to interrupt a good engineering-geek conversation with a practical question, but what's the voltage tolerance and range of your cat? Is there any way it can come in contact with the existing wiring or the modified power source?
As a cat owner, I had several thoughts and reservations about the whole thing from the safety of the toy in general to the safety of wiring it with something resembling part of the very toy being modified, but I've learned my lesson with that sort of thing and him. For the sake of peace, I'll just share what he wants to know and leave it at that.