The company that manufactures Glacier Bay toilet products, North American conglomerate Foremost Groups, doesn't sell these products directly. It distributes them exclusively through Home Depot, which is where you should go if you need a brand-name replacement part for your Glacier Bay toilet. You may be able to use a generic replacement part, though, and in that case, you can probably get it at any hardware store.
Finding Your Toilet Model
Before getting in your car and driving to the nearest Home Depot, start your search by visiting the home improvement outlet's website, specifically its Glacier Bay toilets and seats. If the preceding link doesn't work, click to the website's home page and hover your browser arrow over "Bath & Faucets" in the Department menu on the left of the page, then select "Water Saving Toilets". When you click on that link you'll come to a page with a drop-down menu labeled "Brand." Choose "Glacier Bay" in that menu to arrive at all the Glacier Bay toilet models currently available at the store. Find your model in the list of options.
Shopping for Parts
Knowing your toilet model name and number will help you locate the parts you need when you get to your local Home Depot, but be prepared for the possibility that the manufacturer-supplied parts aren't in stock. A sales clerk may be able to order them for you, but in most cases, you'll have to settle for parts from other manufacturers. For example, Glacier Bay toilets often feature third-party fill and flush valves. It helps to bring the defective part with you so you can visually identify a matching part, or at least one that will work.
Most Parts Are Generic
The only parts of a Glacier Bay toilet that you can't replace with a generic product are the bowl, tank and lid. The bowl conforms to standard dimensions, and any seat will fit it. Moreover, you can use flush and fill valves other than those specifically recommended for Glacier Bay toilets, because the water inlet holes and flush openings in the tank have standard placement and dimensions. Similarly, the water supply hose is a standard one with a connector that fits any brand of fill valve. If you had to remove your toilet and reset it, the wax ring and bolts you need are generic.
Replacing Cracked Porcelain Parts
If the tank, bowl or lid on your Glacier Bay toilet should crack or break, you'll probably find it easier to replace the entire toilet than trying to find a replacement part for your existing toilet. Home Depot doesn't stock tanks, bowls or lids for the Glacier Bay toilets it sells. And although the customer service department may be able to order one, it may take up to a week for it to arrive, and you may end up paying as much for it as you would for a new toilet.