Try this link -- at least in the east, this is available immediately
Kem-Tek Pool and Spa All-in-One Concentrated Chlorinating Granules @ Amazon
Note that this is the 5# size; other sizes should show up as well. The 25# size is also available, but the 12# size shows a 2+ week wait.

We're finding it VERY hard to locate un-diluted dichlor. The only reliable local source we've found is Sams Club. The dichlor they sell (24 1# packs or a 50# bucket) is at an excellent price, if available. The dichlor commonly sold at Kmart, Walmart, Lowes and Costco, as well as at most pool stores, is blended or diluted.

In some markets, Home Depot sells the same Kem-Tek product you'll see if you follow that link. If you can find that, it should be OK, too, though probably no cheaper than Amazon.

The "HTH Chlorinating Granules" (your link) is calcium hypochlorite that is heavily diluted with magnesium sulfate (Epsom salts) (MSDS at Home Depot)

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