Do you want working or non-working signals ?
If you want working signals, I highly recommend Scale Models Division. SMD's owner/president, Serge Lebel, handcrafts working brass signals at reasonable prices. Custom work is also possible.
While he does not have a web site himself; he does have a US distributer (based in Florida, I believe) who I've been told will feature SMD products on a web site. Unfortunately, the only contact information I have is Mr Lebel's address and phone number. If you contact him, I am sure he can answer your questions.
I have had Mr Lebel build a custom signal bridge for my layout. It came ready to install, fully wired with LEDs and resistors. The quality of his work is extra-ordinary.
I've also had the opportunity to meet him on three occasions and found him to be friendly, helpful and accommodating.
Other N-scale products available from SMD: laser-cut building kits, and etched brass detail parts. In HO, he offers laser-cut building kits.