Are you waiting for Black Friday and Cyber Monday to get started on holiday shopping? You might be making a mistake. Some gifts that are expected to be popular this year probably 1: won't go on sale and 2: will probably sell out.

In recent years things like phones, smart watches and fitness trackers are best purchased when you find them.

"The Apple devices are gaining popularity, so if you're looking to get the new iPhone or Apple Watch, I'd recommend getting those now," said Sara Skirboll, a retail trends expert with the app RetailMeNot.

"History tells us that those items might not go on sale anytime this year."

I checked prices throughout 2017 and found prices for the following tech products to hold steady week after week:

GoPro Hero 6

All Apple products

FitBit fitness trackers

I also found that despite a lack in discounts, those items have sold out in previous years.

Amazon's Echo Dot was 2016's hottest product and retails for $49.99. From time to time you can find it $10 cheaper. Last Christmas even Amazon had trouble keeping them in stock.

"If you're looking for any type of electronics that are topping the tech lists, I say get out there and get them now because you don't want them to sell out," said Skirboll.

Retailers I've spoken to said the iPhone 8 is generally in stock but supplies do run low between deliveries from the supplier. The iPhone 7 is selling exceptionally well since the release of the newer 8.

Perhaps many people who would have purchased the iPhone 8 are waiting on the next version, the iPhone X. If you have that device on your gift list you'll need to get busy before Halloween! Pre-orders of the iPhone X begin at midnight Pacific time October 27th. It is widely expected to sell out shortly after they go on sale and supplies are limited going into the first quarter of 2018.