Ebay, Craigslist, yard sales.
Fixie bikes, short for fixed-gear bikes, typically do not come with brakes. Riders control their speed by pedaling backward or using their legs to slow down. Some fixie bikes may have a front brake for safety reasons, but it is not common.
On craigslist
To customize fixie bikes and make them unique and personalized, you can consider painting the frame, adding unique decals or stickers, upgrading the handlebars, seat, and pedals, and installing custom wheels or accessories. Additionally, you can choose a distinctive color scheme or theme to make your fixie bike stand out.
Don't think you can, unless you pay someone to build you a 24" wheel round a fixie hub. Fixed gear bikes are almost only used for road/track cycling, while 24" is MTB DH/ Dirt territory, where a fixie would be really awkward. Easiest kludge is probably to find a bike with 24" disc brake wheels, then slap on a Tomicog. I'll post a link about them. Remember that you need to ditch the rear derailer, and that the frame has to have horizontal dropouts.
Try Craigslist or yard sales.
A vertical dropout fixie bike offers advantages such as simplicity, low maintenance, and a direct connection between the rider and the road. These bikes are lightweight, efficient, and provide a unique riding experience with a fixed gear and no freewheel.
You can find cheap pocket bikes for less than 200$ online at sites such as minipocketbikes.com and other trusted sites. You might be able to get a good cheap one craigslist or ebay.
You can find exercise bikes for cheap on eBay they are normally new or used or you can buy them new in argos or some others exercise shops. Exercise bikes are very popular so they aren't hard to find.
Chubby's Cruisers is a website that specializes in selling parts for cruiser bikes. They can be accessed at www.chubbyscruisers.com.
One can purchase cheap speedway bikes at many retail locations, both in person and online. Examples of such locations that sell speedway bikes include online bike retailers or online auction sites such as eBay.
A fixie bike, short for fixed-gear bike, is a type of bicycle that has a single gear and no freewheel mechanism. This means that the pedals are always in motion when the bike is moving. Key features of a fixie bike include simplicity, lightweight design, and direct connection between the rider and the bike. Fixie bikes are known for their minimalist style and are often customized by riders. In contrast, other types of bicycles, such as geared bikes, have multiple gears and a freewheel mechanism that allows the rider to coast without pedaling.
U can buy one on Craigslist (used)