If you want a "real" Throne chair, your best bet is
this replica by Design Toscano, one of the top creators of historical replicas. It'll cost you only $2,600, a fraction of what some medieval monarch would have paid.
Design Toscano, who makes this replica, says that this chair was "originally created for Lord Thomas Stamford Raffles, who founded the British colony of Singapore". I don't see any evidence that Sir Raffles ever actually sat in a chair like this, so I'll chalk it up to a overzealous copywriter at Design Toscano. Sir Raffles did live during the Gothic Revival period, so it's certainly possible that this particular concept of what a medieval throne would (or should) have looked like came about during that time.
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If $2,600 for a Throne is too much for your blood,
there's always Alibaba, who can get you a chair for under $400. If that's too much, you could always get some
dollhouse furniture from Etsy. :)