Often on T"u BiSh'vat people like to eat members of the shiv'as haminim - the Seven Species by which the Land of Israel is praised. Some of them, such as grapes and dates, are easy enough to come across in their unadulterated forms. But when it comes to wheat and barley, people often resort to cooked or baked grain derivatives rather than consuming the fruit in its pure form. Where (preferably in the U.S.) can an average consumer easily get hold of grains of wheat and barley straight from the stalk?
You can buy plain pearled barley in the grocery store, usually near the dry beans. Many people use it for cholent. You can certainly cook that up plain as a starchy side dish, and you might be able to roast it. Are you hoping to eat it raw?
Wheat berries are easily found in health food stores as well as on-line. I also believe that bulgur wheat should work for you as well, and this is probably easier to locate in stores. Just soak it in water a bit, and you can eat it.
Pomegranates are easy to find in many produce sections around August & September, especially. The other items - barley (as mentioned above) and the whole fruits - grapes, dates, figs and olives are easy to find. I recommend fresh figs over the dried ones, esp. if you get them right off the tree. You'll never want to eat those dried ones again! (My neighbor has a fig tree. But ask any Israeli what fresh Israeli figs taste like!)
Fresh uncured olives may be a bit tricky to find in much of U.S. I guess they're common in CA. In Israel, of course, it's one of the prized possessions, and you see loads of them in the summer.