Weston replacement vacuum food sealer freezer bags are usually bought in bulk and they're relatively inexpensive. If you have a Weston food sealer you are better off not buying the cheap discount bags from other brands. Since you own the best, you should purchase the best quality bags or rolls for your Weston vacuum food sealer.
Bags can also be reused a couple of times if they aren't damaged and if you wash† them out cleanly. The type of bags that you choose to buy are going to be determined by the type of vacuum food sealer that you have. Some can use a universal style of sealer bag while others require ones that matches a specific size, shape, and quality. The biggest choice you need to make when purchasing them is whether to buy in plastic freezer rolls or bags. While bags are great, rolls give you more flexibility in the size. The width is determined by the size you purchase, however, the length is what ever length you cut the roll.
So, your biggest decision when buying Weston replacement vacuum food sealer freezer bags is whether to buy in plastic bags or rolls.
†Do not reuse bags that have been used for raw meat to prevent cross contamination.