Nice find. Likely an orphan, though. See if you can find the trousers in the ladies section. Should be easy to spot in that pattern, and with "Paul Smith" on the waistband.
A few things to know about Paul Smith: First, generally considered a "fashion" house, though I think the Mainline suits (just say "Paul Smith", not "London") get some respect around here. Same with their Japan stuff, I think. Half canvas at best (and that's Mainline), iirc. "PS" is their bottom rung diffusion line.
Also, different suit models have different cuts. All are, in my experience, slimmer than normal. But Westbourne and Byard are particularly slim, iirc. I found a nice 42R Westbourne navy pinstripe once -- actually the only pair of trousers I've ever reunited with a jacket at a Goodwill. But alas, I looked like Chris Farley from Tommy Boy in it.