You can purchase same remote included with the current ultra for $29.99, its the second remote down on this page:
I need a replacement remote for the 4640x. Is it still the second one at this link for half the price? Or is it now the third? Or is it still on this page at all? https://www.roku.com/products/accessories/player
Yes, it now the third down, the Enhanced Voice Remote, still $29.99.