Lost ,have you tried a large dia solid jockey wheel, I too push mine around on the concrete ,and it only take a good push to get it to turn from a standing start,and once it's rolling its not too bad at all
This is on a Kimberly too ,so there is a bit of bar weight upon it
If you want I have a spare , or you could call in at home and give the camper a push to make up your own mind .give us a pm
Cheers. Graham