I'm not a panromantic homosexual myself (I'm asexual), but I think there are good reasons why it can be difficult to find others who identify that way, and it doesn't necessarily mean that it's something out of the ordinary. I doubt anyone really knows how common or uncommon it is. But even if they aren't the most visible, they definitely exist: http://whisper.sh/w/MjU0NjE4MTE1
The reason it's so much easier to find panromantic asexuals, for example, is that asexuals basically had no choice but to adopt the "split attraction model" (since experiencing any kind romantic attraction means having to separate romantic and sexual orientation).
But this splitting is not accepted across the entire LGBT community. It's still pretty controversial, and tons of people refuse to accept that it's a real thing, despite people explaining over and over that this is how they experience attraction. That means many people who would otherwise identify as panromantic/biromantic homosexual, might decide to simplify and call themselves bi. I have personally known one such person.
You should be able to find people talking about these kinds of identities in both asexual and bisexual communities. There are plenty where you would be welcome, even if you aren't specifically ace or bi.
I wish you luck and hope you find what you're looking for <3.