Phil's Old Radios recommends visiting pawn shops, flea markets, swap meets and second-hand stores to find vintage radios and radio parts. Online sites such as eBay and Craigslist are also potential sources for vintage radios, though you need to be careful to avoid a fraudulent purchase. Websites that specialize in vintage radios are another option for purchases and information.
Seek out radio clubs that are local to you, because they can be great resources for finding vintage radios. You may be able to buy or trade with other club members. Antique shops are other places to look for radios. Specialty shops are more likely to have better selections, but you can get lucky finding a radio in a general antique shop that other radio aficionados have not located yet.
Storage unit auctions are another potential source for vintage radios, because the items being auctioned have been stored for unknown amounts of time and nearly anything could have been stored in the unit prior to it being cleaned out for non-payment.
Check classified ads regularly as well, because you never know when someone is cleaning out an attic or had a relative who passed and is looking to get rid of a lot of older stuff, including radios. Garage sales are useful for this purpose as well.
Ask around with friends, family and co-workers too, because they can hear about a sale or a lead that you would have missed if they had not told you about it.