There seem to be very few isolated PSUs that will slot underneath the shallow depth Pedaltrain boards i.e. the Nano and Metro series.
I've been using a Ciocks DC5 which does fit snugly and easily as you can see below and has the outputs helpfully located at the 'ends' rather than at the 'side'.
I've failed miserably in keeping my pedals to a compact Nano+ board (in the picture) and have taken the plunge to upscale to a Metro 24 (with hard case for added protection). I've got a fair few