Hi Swede and
to the forum!
I haven't seen the canisters anywhere but I know alot of guys use Rotella in their engines including me. Rotella doesn't have the zinc it used to have though (Thanks Obama!) so I use Archoil friction modifier in it too. Doesn't take a whole bottle, just a bit of it.
The spin ons I think are the same size as the smaller engines, just deeper so if you find someone with a spin on adapter for sale it should fit. BBV6 or Barry can tell you if that's different.