Don't know about pigeon traps, but I posted an ad on craigslist said I was searching for unwanted pigeons and there were tons of people that said I could come and catch their wild ones in the barn, but then I finally got an email from 2 ppl, 1 was a guy that said he had 43 pigeons that were in his coop and after 25 yrs of raising them he just wanted to retire from it, so he gave them all to us for free, and then the other person said they have too many and are giving us 20 pigeons, lol, I honestly only wanted about 5 for training, but now I am thinking of just raising them and selling them really cheap to dog trainers.
BUT maybe if you post an ad looking for some, you just might get lucky.
Other than that, when we had to trap them before, we would just wait till nightfall and use a long handled net and snatch pigeons up in barns while they were in for the night. You just kind of catch them off guard.