Online and in-person transistor radios are plentiful. Here are some of my recommendations-
Join a radio club- Not only are local radio clubs a great place to meet new people that have the same interests as you, but you can also attend the swap meets. At my local club, there are many tables with transistor radios, many Tube radio restores will not bother with them so they will put them on their table for short money.
Hamfests- Even though Hamfests generally have less AM radio stuff you still might be able to find a transistor radio or two, you will also get to meet more people interested in the hobby.
eBay– Possibly the most popular online option for buying and selling, Thousands of radios on there at any moment. Make sure to check sellers’ feedback and ask questions about buying, since eBay is so popular there are many, many radio collectors. Prepare to be outbid.
Etsy- Some fair deals if you know where to look, Etsy attracts more people that would like to have an old radio as an expensive display piece rather than an item to use.
Radio attic- A growing site that’s been on the internet forever is Steve Adams Radio attic, dedicated entirely to radios. For serious radio collectors.
Craigslist & FB marketplace- Sometimes you can get radios locally for cheap from people who are clueless and will ask for very little without going very far. Though use common sense and caution for those listings that are too good to be true.
ARF- what’s ARF you wonder? Antique Radio Forum has a classified section for members, where you can buy and sell radios and parts. Not to mention it’s free to buy & sell!
73,
Henry