Sure there are. I was saying that for some of us, the ROI on "going to the junkyard" vs. mail order is negative. That's why there are alternatives.
Sure, but I'm in Canada (you aren't, according to your profile). Ordering online is a whole different kettle of fish, because so many sites are in the US. Not only is currency conversion an issue, there are extra shipping charges, possibly customs and border charges, and taxes.
It may not be worthwhile to make a trip to the junkyard for just one cap (assuming you don't find it interesting to visit a junkyard and see what's there), but in the yards I'm familiar with, I can pay $20 or $40 for a bunch of different smaller items that would cost hundreds of dollars ordered online individually.
For the OP, if you want a new cap, here's a Canadian site which can sell you a new one for $20 plush shipping:
Brake Master Cylinder Reservoir Cap OEM SAAB SAAB Part# 93189060, 93172094 Fits: 9-3 (03-11) exc. (03) CV OEM SAAB Part
nordicspeed.com