I used one with DD, but got it when she was about 10 months old and she was on a cub saddle by the time she was 2. Pony was too doddery by the time DS came along, so he didn't ride till he was about 18 months when we got a new pony, but he was fine from the start with a normal saddle (had to ride on whatever his big sister had been using!) The basket saddles are fab, and I did use the old pony as a pram with one, but you don't get a lot of use out of them before the child is ready for the next thing up. I bought mine new, and sold it 18 months later for nearly new price.
The only ones I have ever come across were actually quite big. They might be too long. You could search Ebay for one and try it for size. They do seem to hold their money so you could sell it on if it was no good.
I was wondering if anyone had used one and how they got on and what age the child was when they moved to a proper saddle. My dd is 15mths she loves the horses. But I was wondering if we could use the pony as a 4legged pushchair?
Does anyone know of or has one gathering dust that they would like to sell. That would fit a rather compact standard shetland.