Do you mean "old" or "old style"? You can get old Sturmey Archer 3-speeds on eBay, or on thousands of old bikes where ever old bikes are sold. I've seen a number of old, 3 speed bikes on Craigslist, and bought one of them.

As for "old style," Sturmey Archer still makes a 3-speed hub (maybe), that, from what I understand, is pretty much the same basic design as always. It's one of a dwindling number of new hubs that can squeeze into old, narrow drop outs. I've been in the market for one because my Craigslist bike came with a 28 spoke wheel, and I want to go 36. The problem I'm noticing is that I'm not seeing Sturmey Archer hubs in stock many places anymore. They mentioned in the spring that they were changing the 8 speed hub and, I think, reintroducing the five speed. I'm wondering if they are letting current stock sell out in anticipation of a new line of hubs that should be out "early this summer" according to their website.

But it may depend on what you're looking for. I was specifically looking for a 3 speed coaster brake and the dynamo/drum brake front hub, both of which seem to be becoming scarce quickly. Other models may not have that issue.

For my part I currently have 3, old, 3-speed hubs: a Shimano 3CC, an SA 3SC, and a Fitchel & Sachs Torpedo. None are currently in use, but the SA and the Shimano both worked fine last I tried them (false neutral in the SA, but I believe that's a problem a little cleaning usually solves). The Sachs I'm still looking for an indicator pin for, but it appears to be in working order otherwise. I know that's germane to the OPs question, but it does speak to the longevity of IGHs in general.