I don't recommend the Mirliton mini... I have it and the bear and the dwarf are a solid piece of metal, hard to convert.
Here is a link to a DakkaDakka thread about Valhallan Bear Cavalry Rough Riders. The author used DeeZee Miniatures bears and the scale is perfect.
I have found a unit of dwarves riding bears
here... the author used a mix of Mirliton and Reaper minis, so you can check the scale.
Reaper has a good line of bears (Dwarf cavalry), even if they are a little expensive. Since the rider is a separate piece, they won't be too difficult to convert.
Here are some links:
- Animal Companions -
link
- Dire Bear -
link
- Ursula, Dwarven Bear Rider Captain -
link
- Dire Bear 2 -
link
- Thorondil of Kragmar -
link
- Thorvald, Dwarf Solo -
link (this mini is great!)
- Dwarven Bear Cavalry -
link
Hope this helps, and post some pics once you have converted something!