Try looking at the UK sites !! I doubt if you can find matches but you may find similar chairs !! Most people don`t stop and think about why there is only one like the side chair !! Chances are it was once part of a set for a dining table !! English furniture styles have always been ahead of the U.S. and whatever was popular there arrived here later !! So many things in the Victorian era were being tossed when its popularity was strong here !! Later in the 1900`s it was just used furniture in the UK but being sold as antique here by many shops !! When the antique market was very strong here in the 70`s,,furniture was purchased for pennies there and shipped here for resale and some made quite a bit of money refurbishing and reselling these pieces !! There was no interest in keeping a set together so if someone wanted one chair,, they could get it !! As far as your side chair, they may have bought 4 or 6 on the same kind and due to the way they were handled, ( I have actual knowledge of this) they may have 2 or three that were not too damaged to sell !! So it was easy to purchase a single item !!
I used to buy from a dip strip shop in the next town and I have seen beautiful furniture literally in piles half way to the roof of their building !! I tried to get there when the trailer arrived but didn`t always manage it !! That is why especially in the south there is an abundance of English furniture on the market !! Sorry for the length of this but thought it might help !! Yours may not be English but its worth checking !!