You may purchase a usb wifi adapter which may be more reliable than your laptops built in wifi or you could look to "DIY" solutions such as increasing the range via altering the antenna on said usb adapters this is legal in most areas and is effective.
projects such as the "cantenna" might assist you.
First You have to understand that why we are using wi-fi booster in the laptop , it increase the data transfer rate between two wireless devices , we can find it from the websites
You can find those at any major hardware reseller. The thing you are looking for is called a repeater. Some access points also have a repeater mode, there is pure repeaters too. If your wifi card has an external antenna jack you can also try to connect a better antenna.
A good place to buy a wi-fi booster would be at Fry's Electronics or Best Buy. If you want to search online, you can check out Amazon or New Egg. Laptop computers sometimes come with slots called ExpressCard slots. Some companies produce wi-fi boosters that will fit specifically in these slots.