I have the Eskimo Redneck 1 piece ice chisel. It knocks ice out very well and costs $39.99. There are plenty of sales on at the moment so you'll get one cheaper. Also check out the clam ice chisels there are also on sale - saw one for $19.00 at Sportsmans Direct. Both are 11lb.
Before I bought my chisel I had a spud bar from Home Depot - it was ok, heavy and the head profile did not really chip out the ice. It was often difficult to pull it out of the ice. Several times I ended up cracking the ice as I tried to lever ithe spud bar out of the hole (not a good idea).....