Looks like I'm a literal day late here, but still figured I'd add to the discussion with the following:
For a 3" BBZ, the closest matching nose cone is likely the Estes PSII DBRM nose (072304), mentioned by
@kuririn and several others. The PNC-60AH nose cone is similar in shape to the PNC-55AO, but for a given diameter, is slightly longer. At 3", an upscale 55AO should be ~11.3". The 3" AH is ~12.25, so roughly an inch too long.
@heada, Randy teased the upscale BBZ at NARAM-61 in 2019. I first heard about it when listening to Rocketry Show podcast archive releases. eRockets released a Pro Cherokee 2x upscale earlier this year. I emailed Randy about the BBZ upscale in September; this is his response:
"The Blue Bird Zero has been delayed, we originally wanted to issue this with a Balsa Nose Cone, but the shortage of quality balsa has removed it from the list of possibilities. We are in the process of bring in a large number of 3D printed parts, we will now 3D print the nose cone when we do release it."
I assume the Pro Cherokee was released in its stead, as it uses a not-to-scale aerotech nose cone. I also took this to mean that the BBZ is still in the release queue, just delayed until they can print nose cones in quantity.
From my understanding, in addition to a printed nose cone, the "Pro Blue Bird Zero" will use heavy wall BT-80 like the Pro Cherokee.
@rklapp , perhaps I am misundeerstanding, but if you plan to use the PS II BDRM 3" cone with 2.6" BT-80 tubing, that will prove difficult.
@Jtgreig , The BNC-80HX nose cone is 8.1" long, according to the website. While I have seen the measurements on eRockets to be incorrect for some upscale/downscale noses, if that is accurate, you may want to add a couple inches to your airframe calculation. A 2.6" AO would be around 9.8" long.
I've also attached a fin template that compares the original BT-55 Red Max and BBZ fins. This template was made using the openrocket sims for each model made by K'Tesh. Red Max is on the left, BBZ on the right. While they are somewhat similar, the Red Max fins are slightly larger, and the BBZ has a different trailing edge sweep.