Dremel makes a version of their 2-speed cordless Minimite rotary tool for carving pumpkins. These are not with the rechargable battery. Rather they are powered by 4 replaceable AA batteries. It takes all of the standard 1/8 inch shank burrs (Dremel and other manufacturers). The low speed is good for drilling plastic & resin, and the high speed is fast enough to grind without melting the plastic (a problem with high speed grinders). Instead of the basic black, these Dremel grinders come in a translucent orange.
These pumpkin carvers are currently for sale at Lowes hardware for about 25 bucks. Two years ago I picked one up after Halloween for half-price. Check your local Lowes, and make plans to go back after Halloween to see what kind of deal you can get.
Dremel also packages this AA battery powered tool for golfers, to clean & polish their clubs [and to sharpen their spikes?]. It is translucent green. Check your local golf pro club or store for this one. You might not find it on sale as easily.