Sierra Marine has been in business for what seems like forever. The product line is extensive and they are considered to be one of the largest aftermarket parts suppliers for the marine industry. Virtually any boat part can be found in their catalog with only a few left requiring a purchase of an OEM component.
Recently, they were acquired by Teleflex which is also a leader in the industry. The product has not changed though and most marine distributors and wholesalers will carry Sierra marine products. Even the big stored will most likely have the catalog with an order system but also will charge full list price for most any parts.
The main warehouse for distribution is located in Illinois and some special orders are possible. Keep in mind, they do not sell directly to the public and sometimes multiple distributors are used causing more time to fill some orders if they are considered to be a special order. They are usually responsive and do fill orders as needed sometimes shipping directly to the customer eliminating a few days lead time at least.