Whichever company vacuum you take, a 12v vacuum cleaner will never have the power of a 230v household one. If its possible drive your car close to your home and use an extension and the home vacuum to clean it
If you must have a 12v cleaner, go for the one from Black & Decker below Black Decker Portable Handy CAR Vacuum Cleaner FOR ANY CAR 12 V ACV 1205 | eBay
There is a cheaper version of this without the pipe and accessories but go for the more expensive one with those accessories. Its worth the money.
Also a small note- prevention is better than cure. If possible, have your carper washed and your car cleaned at the service centre and then have them laminate your carpet in leatherite type material. Its much easier to clean your car then, so it will remain clean