Kerrisdale will order that film for you. They won't stock it, because it is hard to sell.
I can guarantee that Kodak Alaris pays Eastman Kodak the same amount for the film, no matter where it is going. But the amount that Kodak Alaris charges to then sell that film to the different distributors in the various corners of the globe will vary greatly, depending on factors like shipping and importation costs and size of order.
I'm pretty sure that Harman sells a lot more black and white still film than Eastman Kodak does. And Harman products end up going eventually to far fewer retail destinations than Eastman Kodak film products go to. For those reasons, Harman has elected to go the exclusive distributorship route, while Kodak Alaris will sell to multiple distributors, who themselves could end up keeping prices low through competition, but don't always do so.
The exclusive distribution route has advantages and pitfalls. Harman knows a lot about the pitfalls. When their US distributor (Wynit) suddenly went under, it left them with huge problems and, I suspect, a huge amount of uncollectible receivables. As the US is Harman's largest market, I suspect that Wynit's collapse may have come close to putting Harman out of business. Kodak Alaris' choice of multiple competing distributors avoids that particular problem.
In the case of Amplis, I'd be surprised if their exclusive distribution agreement with Harman doesn't prevent them from distributing Kodak film, or for that matter any other competing brand of film. I note that their list of brands doesn't include any other film brands.
And additionally, and quite frustratingly, it is my opinion that the big New York and California internet retailers are not particularly healthy for the industry. So much of what we price using them as the comparison they sell at incredibly tiny margins - margins that will not support even the most efficient of small retailers. Andrew Bacon has posted here that he, as a retailer entitled to purchase wholesale from Harman's current exclusive US distributor (the distribution part of Roberts Camera), essentially pays the same or very near to the same wholesale price as B&H has as their retail price. Small retailers can't survive on 1 or 2 percent margins!
FWIW, my sources indicate that Eastman Kodak, for one, is currently being slammed with increases in costs, shipping difficulties and difficulties in obtaining critical components in a timely manner. As an example, the cost of the cellulose triacetate support for most of our films has jumped incredibly, and there is a real shortage of supply. In addition, they are faced with a desire to increase their workforce in a market where it is difficult to hire qualified staff and their salary demands are significantly higher than two years ago.