PIV are indeed rare beasts. If you don't wanna search for long time (you might get lucky though who knows), you can get an
Indivision 4000 SD/FF along with whatever RTG you may find, and switch with a
UMON RTG/AGA switch from AmigaKit, or for a little worse quality an KVM switch. That way you got 1 output for your Monitor and 100% RTG/AGA modes (with only glitch... that you have to use a switch)