I have had a Bucket Solutions " Universal Quick Attach Bucket Spade " since February 14, 2012. I thought about attaching a bow and giving it to my wife as her Valentine's Day gift, but reconsidered. I bought her flowers and took her to lunch instead. The Bucket Spade cost was $369 delivered from the factory in Colorado to Florida.
Bucket Forks, Tractor Forks, Loader Forks by Bucket Solutions
This is a high quality, heavy tool, probably around 100 pounds. It is shaped like your garden spade (duh), it is sharp, it attaches and stays secured to your bucket with a crescent wrench and I am sure the weight helps considerably to make it effective piercing dirt. I soon learned to store it on a Tractor Supply garden wagon so I could move it to the bucket and maneuver it onto the bucket easily. (I am 64 years old.)
I have excavated two holes: one 4' diameter X 3' deep, the second 4' diameter X 4' deep in Florida sandy-loam containing Water Oak roots. There is a learning curve here....much of the time the spade is hidden behind your bucket so the first hole went pretty slow. By excavation #2 I learned instinctively where the spade was positioned and the second hole went 50% faster.
The first time I removed the spade a little (aluminum?) screw which fastens the pad to the securing bolt fell out onto the driveway. I rubbed a little beeswax on the screw-threads and replaced it. I doubt this screw will fall out again. Either beeswax or Loctite should be applied to the right and left side pad securing screws at the factory.
I think this implement would serve your need well. I am attaching several photos. Unfortunately my camera battery died in the driveway before I photographed the excavations....always the way......
Bucket Spade is mounted on bucket of my Kubota B3300SU Compact Tractor/Loader package. (33 horsepower)
The Customer Service at Bucket Solutions is courteous, helpful and accurate.
Delivered on the day promised when ordered.