there are many cheap pcie 1x options with 2 ports
asmedia (asus subsidiary) and marvell make the chips for these
almost all of these are supported well in windows and linux and cost about $20
like this
syba, koutech, and others make them too
if you want a single card
4 port pcie 4x would be a good option
you can get lower prices if you are willing to forgo sata III support
I dunno if any of these fit the bill for you.
only a single 1x pcie slot available ?