Have you contacted vet offices and low cost neuter/spay clinics? Since he is intact and someone may be keeping him, the finder may go and have him neutered.
Jennifer
This is a crosspost....
Becks got out of a dog park yesterday in downtown Houston near Minute Maid Park.
Male, 25 pounds, red & white, 8 years old, microchip 497F5C320C & 276097202160769
We just flew in from Germany for the 4th.
He's wearing a green nylon collar with my Germany phone number
I saw a post on FB that he is back with his owner now.