One thing I have done is reserved my business name's .com and I point that web address straight to my eBay store page*. That reserves the name for you, points people to your inventory (you could point it to whatever other site you sell more on instead, if it's not eBay), and gives you the option in the future to create your own site if you want to.
Buying a domain name is cheap, and well worth it to keep from kicking yourself in a few years when you really want to do something with mycoolstorename.com.
*I have not checked that linkage in awhile, turns out it's defunct, lol. Doing online chat with godaddy right now to get it back in place. See, these threads are quite useful, they remind me to check things like that from time to time!