Q: I've been trying to order a jHub Ultra power bank since your column ran in early December. The manufacturer's website says "sold out," and it does not show up on Amazon. How do I get it?

A: I received many e-mails like this in December. I am partly responsible for your inability to buy the product, and it is quite a story.

For those who missed the previous column, a power bank is a rechargeable battery pack that can be used anywhere to charge cellphones, tablets, cameras or anything else that charges via USB. I've tried many power banks over the years and have never been happy with any of them, finding them to either lack meaningful power capacity or be too big to fit in a pocket, making them difficult to carry. The last small one I tried had only enough power to take my iPhone 4S from 10 percent to 60 percent.

Along comes the jHub Ultra power bank. It's small, sleek and has enough capacity to completely charge an iPhone 6 twice, all for under $15. I recommended it in my column and announced plans to get Sound Advice logos printed on them for a new weekly giveaway.

A month after that column ran, I evaluated many other power banks at the 2015 Consumer Electronics show, and it only served to confirm my initial impressions. Nothing else has the same combination of size, weight, power capacity and price.

Readers started e-mailing me when the product disappeared from Amazon and the manufacturer's website said they were sold out. I contacted Brian Varner at Modern Portable, the manufacturer. He explained that when my column ran, a large quantity of orders suddenly came in. The spike in orders sold out existing stock and triggered a red flag at Amazon called "velocity limits," a fraud prevention measure that monitors sales growth over time.

Though Modern Portable had done nothing wrong, exceeding their velocity limit automatically removed their products from Amazon, suspended their account and flagged it for an audit. The review took several weeks to complete. (You can read about Amazon velocity limits and account review at: http://tinyurl.com/amazonvelocitylimits.)

This course of events made it impossible for Modern Portable to take orders for almost the entire holiday season. They have been really good sports about everything, but they lost a lot of business, and I think they were dealt a real injustice.

The good news is that jHub Ultra is back in stock, Amazon is satisfied that nothing crooked was afoot and everything is back online. Am I risking causing more chaos by recommending the product again? Modern Portable said that Amazon raised its velocity limit significantly, so ordering should not be disrupted again.

I certainly meant well. Publicity usually is a good thing, for both the companies making good products and the readers who want to buy them. Although my role in this saga was completely inadvertent, I do feel bad about what happened. I would like to ask readers who have any interest in a power bank or other charging products to please visit www.modernportable.com or www.noplugnoproblem.com and check out the jHub Ultra. Hopefully, some of you still want one.

Send questions to Don Lindich at donlindich@gmail.com. Get recommendations and read past columns at www.soundadviceblog.com.