I tend to think, having been in the advertising "hype" business for some time, that some of those "Only 5 Left", etc., are there more to get potential buyers to pull the trigger rather than anything else. Certainly, there are sometimes shortages in the supply chain, but that is one of the very old tricks in the marketing field to get "on-the-fence" potential purchasers to make the decisive move. We've all been exposed to one form or another of this sales device. "Limited Time Only", "While Supplies Last", and many other marketing gimmicks.
Not to say that shortages do not occasionally exist, but there are certainly enough dealers at least here in the U.S. that you can find an SDS100 or 200 available for immediate shipment at least 90% of the time. Some manufacturers also deliberately hold back on supply to create demand, and I am certainly not implying that Uniden resorts to that tactic.
As Bearcat Joe pointed out in a thread when someone asked why all units are not shipped with the latest firmware, he pretty much summed it up when he said how impractical that would be with so many units already out of the factory and in the supply chain, in warehouses, on ships, in stores, etc. So for those potential SDS purchasers, I don't think there is any need to panic.