I had much the same problem. The solution I came up with is I stuffed a couple of old washcloths in the ends of the bars with a screwdriver. Pack them in tight to the end. I also bought a pair of foam grips $8.00 and fingerless bike gloves from wally-mart for $8.00, Made a world of difference.
Walmart.com: Ventura Gel Bike Gloves, Large: Bikes, Scooters & Skates
Walmart.com: Foam Grips: Bikes, Scooters & Skates