[sjk]

Anyway, they looks like a grey flannel trouser, and I covet them most earnestly. However, they don't appear to sell them on the site, and I haven't found any similar trousers on any other likely retailers' sites.

Any ideas where I can get my hands on these handsome trousers?

Go back to ralphlauren.com. I think you just aren't looking in the right place. If necessary search on "Regent" or "Harper". One pant is on sale at a deep discount. Remember that the search function only shows you the top 3 or so items... click on the link to see all the items.

If necessary, call one of the stores. These flannels are a perennial staple at RL.

And yes, the better RL stores have a lot of things that aren't available on the website. The website seems to be the portal to sell much of the crappy, mass-produced stuff.