The altars are available for 1,650 yen (US$14.35) each directly from Dreams and through their Rakuten storefront (here and here).
The generic oshi character standees seen in the promotional photos are not included, but any true fan should have no trouble supplying their own item to enshrine.
Design includes feature to hook up altars for members you’d wish would hook up as well.
That’s the idea behind the Oshi wo Matsuru Kamidana (“Altar for Enshrining Oshi”) from Tokyo-based novelty good maker Dreams.