One has to be careful when looking at older quotations and using modern definitions. A "Brog" could have far different meanings than more modern ones.
"We know that Highlanders - men and women - frequently went barefooted in summer and winter - see the 1848 R. R. McIan painting of school children - but when they did wear shoes they were what they called in Gaelic - brogan tionndaidh - and they were made mostly from deerskin and pretty rough and ready. Martin Martin in 1703 wrote "The shoes antiently wore, were a piece of the hide of a deer, cow or horse, with the hair on, being tied behind and before with a point of leather."
To make them, the Highlander would lay his bit of deerskin on the ground - furry side down - place his foot on top and draw the material up around his foot, cut off the excess and then punch holes along the top of the instep through which he would thread deerskin thonging. He would then cut holes in each shoe to let the water out . If he didn't do that, water would lie in the shoes and cause what is known as foot rot or 'trench foot' - a serious condition, which if unattended, could result in gangrene and amputation.
Captain Burt, an English engineering officer, was sent to Inverness in 1730 as a contractor and we owe much to his blunt and often ascerbic descriptions of life at that time. Here he has something to say of the Highlander's shoes: "They are often barefoot, but some I have seen shod with a kind of pumps made out of a raw cow hide with the hair turned outward. They are not only offensive to the sight, but intolerable to the smell of those who are near them. By the way, they cut holes in their brogues though new made, to let out the water when they have far to go, and rivers to pass; this they do to prevent their feet from galling." (becoming sore). Highlanders also wore a higher foot covering - a leather boot of untanned skin, which was laced up to just below the knee. These were called cuaran."
I don't understand why we would expect poor Highland immigrants to want to trade something valuable with the Native Americans, when they were used to going barefoot so often and so easily making their own simple/working shoes that worked as well as moccasins. We take it for granted that poor folk grew their own flax, turned that into linen and made their own clothes out of it. That's far more difficult to do than making their own traditional Highland foot wear.
Furthermore, many/most of the images we have of Highlander Scots come from the 1770's and later and even then they often show everyone barefoot for poor folk. Also, one has to be careful that an early image is truly of a Highland Scot/s and not mixed up with Lowlanders (as is too often done) who as already mentioned were wearing mostly English attire from the beginning of the 18th century.
Now I am sure that just like poor English/British immigrants on the frontier, that some of them had period shoes to wear to church or special occasions, but they took them off when they got home to save them, especially in the warmer months. Of course when Highland Immigrants became wealthy enough to buy shoes, they did so, just like poor English/British Immigrants eventually did.
Gus