http://osborn-reproduction.com/ Phone: (770) 962-7556 Should have the decals. You will have to call they don't have web site to buy from.
I just put a Decals Page on my website over the weekend. 70 -72 stuff but all other years are available as well....... https://www.diecastmusclecars.com/BuickDecals.htm
...(from '71 assy manual) 5910725 is "big pulley" (5.875") compressor, and 5910724 is "small" (5.25"). Some other years use red label...
you might be able to get locally at Dels Air conditioning on North Andrews, 1/4 north of State Road 84.
I'm pretty certain you mean KEL Auto Air. Been going there for 30 years but never thought of them for this. I'll stop by.