What you should do if you are intrested in getting the spells, is to Open the games files with Near Infinity, take a look at the spells.ids file and find if it has the Bigby's Crushing Fist in it, it should be:
2918 WIZARD_BIGBYS_CRUSHING_HAND
Now, if you don't have the 2918 WIZARD--plahplahplah, then you are kinda out of luck in this.
If that is not the case, then you can just replicate it by taking any scroll file you want and back it up using the Export function you get with Right Clicking the file, like say scrlb4.itm which should be the wish -spell scroll, then edit that file by having the View -window open and doubleclick the first "Magical(3)" in the Abilities window.
This will open up the ability, the only Effect it has should be "Cast spell 146", double click that and that will open the window, which one line has the Resource -field, which should select, and dong so should let you to choose another resource, it should be just the previous one, so you just need to go up one in the "elevator" from 919 to 918... and use the Update value -button, then you can exit from there using the X and the go back two windows to the Abilities, edit the second Magical(3) the same way and now you have the replica of your original scroll differently name, and the file is in the overide folder in your game, so you then name it how you like and restore the original scrlb4.itm too.
Edited by The Imp, 07 October 2019 - 03:33 AM.
Yep, Jarno Mikkola. my Mega Mod FAQ. Use of the BWS, and how to use it(scroll down that post a bit).
OK, desert dweller, welcome to the sanity, you are free to search for the limit, it's out there, we drew it in the sand. Ouh, actually it was still snow then.. but anyways.