How can you charge your canon powershot SD790 IS on your computer?

Honestly, you cannot charge your canon powershot with a computer. Last week I lost my charger for my powershot and it's no where to be found. I tried, and tried all week to charge it on my computer. I also looked all over the web. It's no use. But I found a solution, if you go on ebay there is a 2.00 powershot charger with 3.00 shipping, so only 5.00! I'ts not used either so yeah. That's my solution to yours and my problem. Thanks for your time!