For $30 or less, you can have an inexpensive gauge and kit
The dial indicators are fairly cheap and widely available, however what makes it bike specific is the holder.
The dial indicator I use is from McMaster Carr , part number 20715A25 cost: $20.20 with a couple of extensions, 20625A132 & 20625A134 cost $4 ea ( go ahead and get them, then you will have any combination of lengths for the future) It is in inches, not mm however conversion is just math.
I put up a post on how to make a dial gauge holder here:
http://www.dotheton.com/forum/index.php?topic=52940.msg592758#msg592758
Also, your service manual shows to set the timing at 2.2mm BTDC ... just a tiP: this was for 1970's premium fuel. What was 95 octane then, is now 93 octane PLUS now we have that damn 10-15% ethanol! So the 2.2mm is too far advance for today's premium. The consensus among today's RD guys is to set the timing at 2.0mm BTDC