Smallest internal 1 port FXS adaptor?

I’m looking for a small, non expensive but reliable 1 port FXS solution that can be installed within
a computer case (PCI or other, it doesn’t matter). Something similar to the x100p (FXO) PCI would be ideal (No TDM410).
Asterisk will be installed in the PC itself. I thought of hiding/sticking in a USB ATA, is there a better off-the-shelf solution?

Did you ever figure out which one to use?

Nope! I am still looking !