Gloaming Ponder, from Vivant. I think it was pub-only, but I can save a can for next time you are in town if you want, or if we go up I'll bring one. Any later than May 1 and it will be gone, though.
I have had Thelonios! It was in 2015 though and I didn't leave any notes. That's technically not a bock, as bocks are lagers, and don't pull as much flavor from yeast as dark Belgians.
Consecrator for a local, should be easy to find. Ayinger Celebrator, too.
If you want to include dark Belgians (they are pretty similar to me, and fit very well in the early spring drink lineup, where there are still some remaining snow piles, the wind still holds a chill, but the perennials are pushing through, the sun is shining, and sometimes you can shed the light spring jacket...) see if Jolly Pumpkin has any Noel de Calabaza sitting around, or if you want to drop some money look for a Beast Grand Cru from Avery. That last one- see if you can find one that's hung out for a year or two, and plan on splitting a 12oz. The 2016 release was almost 17% abv.
Now a cautionary tale: shortly after I turned 21 and I actually had access to more than Bud & Labatt, I found a 4pk of Lion Imperial Stout at World Market. It was cheaper per ABV than anything else, so that became my go-to beer.
(14 years, but who's counting)
I am shopping for my coffee/milk stout tastings this past winter, and I see Lion Coffee Stout. It remains as the last stout of the year, mid-March, I don't even bother tasting it blind since there is no possible mystery.
One sip, it gets dumped.
It's like "Shorts Brewing attempts a Stout" levels of bad. No, worse. Terrible. Awful.