I like Surly's Stainless steel chainrings in single speed drive trains (Brompton is such)
I have a 38-110 on a bike ..

why 2,? the chainline is awfully close to the frame hinge plate , it will be way off line
if you stick a chainguard flange on there instead.

Cyclocrossworld,com and others has nice ones made for the their purposes
I have one the companion for that 38t 110.. if you feel a trouser guard is needed..

I have not had the chain bounce off (54t,mountain drive crank)
on my Bike Friday Pocket Llama.. i added a 'chainminder'. it fits with a hose clamp
holding on a plastic finger ..


have one on bikes with triple cranks too..