Very Simple.

Go to google.com - Search on the phrases "trade shows" or "trade magazines" - find the exhibitors and find the advertisers.

Go to the library. Get the Thomas Register of American Manufacturers. Call the manufacturer and ask about US Distributors or direct distribution. Ask about minimum order size for first and following orders.

Regarding name brand consumer electronics - the real wholesalers will give you good pricing IF you are doing tens of thousands of dollars per month. Still, the percentage you make is not very high. DO NOT EXPECT 40-50 percent margins - expect more like 3-5-10% for starters. Maybe 15-20% after developing a relationship and building a lot of volume.

Off-brand electronics is another story - look for suppliers on alibaba.com

All done. - You're welcome.