One could purchase a Motorola Surfboard SB5120 cable modem on Motorola's website or other retailers' websites such as Amazon, eBay, etc. It is easier to look for the modem in its own site.
One can find a good deal on an external dial up modem on various stores online and offline. Some stores have sales on their products at various times of the year. Some of the stores are Best Buy, Amazon and Walmart.
A GSM Modem is a modem that operates over a subscription like a mobile phone. One can purchase a GSM Modem from eBay, Walmart, Amazon, and Robot Shop.
With most providers, you will have to purchase your own Wireless modem or purchase one from them.
There are many places one could purchase an external sound card. They can be found in numerous stores such as Best Buy or on websites such as Amazon and eBay.
If you are a resident of the United States you can get it at the comcast website or if you are not a United States resident you can buy from Amazon. Or you could go to your local electronic store.
You can purchase a wireless cable modem router at any electronic store. Or if you'd rather buy one online, you can find one at Newegg.com or Amazon.com or even Ebay.com Those websites are the best in saving. Or you could get one from your internet service provider for a small monthly fee.
You can find a Null Modem Serial Cable for sale from stores such as Walmart, Tiger Direct and Radio Shack. You can also get these cables from retailers such as Amazon.
An Apple USB modem can be purchased directly from Apple through their website. Alternatively, one can find this modem at an electronics store, such as Best Buy or Amazon.
A person could purchase a Vodafone. One could buy a Vodafone from many websites or retail stores. One website is Amazon. One retailer is Best Buy. Another website is TigerDirect.
You can purchase a Fritz!box wireless LAN modem from the shopbot website or from the fritzbox official website. Altenratviely you can purchase one from the amazon shopping website.
One can purchase an external USB firewire hard drive in electrical appliances stores such as Radioshack. In addition, Amazon or eBay will have external USB firewire hard drives.