HDMI to USB converter

First, you need to understand you can't just slap some simple converter on the end of an HDMI cable that will turn it into USB, and make the computer accept it and do what you want.

What you need is a video capture system of some sort. This will be a device that will accept a video input, and provide (or connect to ) software that will allow you to view the video input. There are simplistic USB based ones like the VA11A from X10 which accepts a composite video connection, and works with webcam software. The picture quality isn't great, and it makes the computer handle the processing, but it is simple. Unfortunately, that example is not one that fits your needs... but the point is that it is more than a simple converter.

So... you need a USB video capture system that accepts HDMI. That means that if you start somewhere like at Newegg.com, first bring up all the USB video capture devices. Then, cull the results by looking at only the ones that have an HDMI input. That's how you are going to find what you want.

Unfortunately, because you need an HDMI input, you aren't going to be looking at devices that are limited to small resolutions.... which will translate to your choices not being what most people would classify as "cheap". But, depending on your budget, you might like the prices you see.

UPDATE

• We cannot recommend products to purchase, as this is against the policy at Superuser.
• I presented the link to that specific X10 product because A) it was NOT something you could use, thus it did not violate the policy at Superuser and B) it was an example of how a simple cable converter was not what you needed.
• You did not detail anything about the laptop you intend to use, and most laptops (almost none) come with built-in video capture devices. In point of fact, if the laptop you were going to use did come with a built-in video capture device, it would not be a low-end laptop.
• I detailed exactly what you need to search for, namely "USB Video Capture" and +HDMI. A search for that in Google will present you with a number of devices. At that point, you can easily sift through the results to find the product you wish to purchase. Again, once you are looking at USB Video Capture devices, you would then cull those results for ones that had HDMI inputs. However, I said all of that.
• Again, if you are expecting to see product recommendations, you are in the wrong place. Shopping questions are not allowed.

Short answer: buy a webcam.

I've had luck with BlackMagic cards in DirectShow capacity (what most Skype/video-conference software uses), but I don't believe it is supported. Something like the Intensity Pro line might get the job done, but you're looking at about $200 on the low end.

I pretty much always go with a nice Logitech USB webcam, even on some boxes that already have expensive capture cards in them.

Is there a reason you're intent on the camcorder?