If you need to buy a gift for the kids in your family (or you want to splurge on yourself), it's hard to go wrong with LEGO. The plastic brick sets are as popular as ever; so popular, in fact, that you may have trouble getting your hands on one. Now, the LEGO store is helping customers get the models they need in time for the holidays. As Brick Fanatics reports, LEGO.com will notify you when a sold-out kit you like is back in stock.

The online LEGO store's Black Friday/Cyber Monday event was so successful that they had trouble keeping up with the demand. Buyers exhausted their inventory, with many of their largest sets currently on back order or temporarily out of stock. The Millennium Falcon, Diagon Alley, and Colosseum kits are a few of the high-end models currently unavailable online.

But LEGO fans who had their hearts set on a sold-out item shouldn't despair. The LEGO Group has responded to the issue by inviting shoppers to sign up for email alerts notifying them when a set is back in stock. You can find the button to register on a set's product page next to the "add to wishlist" option.

Many of the sets that are out of stock contain thousands of pieces and cost upwards of $400. If you aren't able to purchase a valuable LEGO set online this year, you may have better luck looking in your attic. Here are eight expensive LEGO sets you might have at home.

[h/t Brick Fanatics]