If you want to try the Balvenie 21yr, the easiest way is to find a Balvenie sample pack:
This is how I first tasted the 21yr, and is the ONLY reason I was willing to pay the entry price for a bottle. If I didn't already know how it tasted (and that I LOVED it!), I would never have paid the bottle price.
The Sample Pack was $15.99, well worth it for a taste of three of the best whiskies in their respective price points: 12yr Doublewood, 15yr Single Barrel, and 21yr Portwood.