Rule V of the 1972 Nemeth Code does not have a braille symbol assigned to this "double struck" font. You may use one of the font attributes not used elsewhere in your document, and explain the substitution in a transcriber's note. Usually the script font is the one that transcribers choose to use. So, yes, go ahead and use that indicator (dot 4) before the English-letter indicator and capital indicator for each of these letters. Your transcriber's note can say something like "Double-struck letters are denoted with a dot 4 before the letter indicator."