I've just received an amazon knockoff ('ecotric') which had 4 star rating. the padding is sponge (not high density foam). it might be okay but I don't advise anyone buying one.
otherwise great for the price and I could always get creative with the padding.

 

Is there a backrest option for the tall boy seat?

 

+1 on that one. Has worked well for years. Looks like the current price has gone up about $50 since I bought mine.