Dates are found in all stores: Amazon, Trader Joe's, Sprouts, Costco and Amazon. I sometimes buy them from Azure Organics — they have a few different varieties. The cheapest organic dates I've found are Ugglies by Joolies — Organic Dates (Amazon) ($25 for 4.4 lbs). The juiciest dates I've found are at Rose International Market in Mountain View (Castro & El Camino). Dr Greger buys dates from Date People! They sell 10+ varieties of dates; they are also available in wet packs.
When I first switched to WFPB, I used to add dates regularly to my breakast porridge. As months went by, my taste buds changed and my need to sweeten my breakfast porridge so much went away. Now I add dates on and off, not every day.
Date sugar is also okay; date sugar is basically dehydrated dates that have been granulated. But I don’t buy date syrup sold commercially (not a whole food; there’s a filtration step involved that removes fiber). Homemade date syrup is okay. For details, see Dates
Can we use dried fruits for sweetening? Yes! I use dried figs, dried peaches and raisins (dried grapes) when they are not available in their fresh form. Generally speaking, dried fruits are discouraged in Whole Food Plant-Based guidelines because we can eat many more dried fruits (fruits whose water content has been reduced) than fruits in their original form (with plenty of water). So I use dried fruits in my morning sweet breakfast sparingly — my objective is to boost nutritional diversity, not sweetness. See Diversity of Fruits & Vegetables for details.