If you're running on a PC, and your sas is prior to v9.2, you can typically use any non-unicode font character you have installed on your PC (for example, font="symbol" '6d'x for the mu character).
But having gone through several versions (v9, v9.1, v9.1.3, v9.2) I don't have v8.2 on my PC anymore, so I can't try it to make 100% sure this will work. (btw - I *really* recommend upgrading to v9.2! - you're missing out on a lot of nice new features!)
Might be a good question for Tech Support, if nobody here can give a definitive answer!