Nintendo, which produces the accessory, has now apologised for the shortages and said it plans to "expand production" to meet demand. President Tatsumi Kimishima said demand for the Plus accessory "far exceeded" the company's projections, noting that production has failed to catch up.
"We launched the Pokemon Go Plus accessory on September 16 to provide a more comfortable play experience for Pokemon Go," he said during Nintendo's earnings briefing this week. "Demand far exceeded our expectations and production has not caught up, leading to product shortages. We apologise to the consumers and distributors affected by this. We are planning to expand production as needed, and will continue to produce and ship additional units."
The Plus accessory sells for $35.
It was originally supposed to release in July, closer to the launch of Pokemon Go. However, the accessory was delayed. In its pre-sales phase, it sold out and started appearing on eBay for prices upwards of $100--some were even on sale for more than $200.
In more recent news, an update for Pokemon Go last week added new functionality for the Plus accessory. With the update applied, gamers can choose if they want to receive alerts for only Pokemon, Poke Stops, or both. Scanning for both will remain the default setting; in theory this should help you catch as many Pokemon and collect as many Poke Balls, which are found at Poke Stops, as possible. But if you only want to search for one or the other, now you can.
For more on Pokemon Go Plus, you can read GameSpot's guide that covers everything you need to know.