Tom:
I was also "bewitched" with the "boom guys" question. (Sorry).
After searching every square inch of my bilge, and inquiring every place I could think of, including this site; I made my own temporary guys out of surplus good quality 1/4" double braid line and a couple of shackles. There is a lot of stress on the guys during the raising/lowering process, so don't use questionable line. Also, I made sure my knots at the deck end of the line could be released quickly under pressure just in case I made them too short! I didn't want to get the mast almost up/down and then have to reverse the process because the guys weren't quite long enough. I will say that after raising and lowering the mast using brute force, following the instructions and using the boom guys made the experience a lot less exciting, which is a good thing. Unfortunately for you, I didn't keep or even measure the length of line I used for the guys. Sorry.