Went back to HL yesterday - no clearance motors....which just means someone beat me to them. As Fred noted, the F15-0 and E16-8 are gone - no hooks any more. They closed out the PSII booster, so no reason to carry 29mm boosters anymore. They only now carry two 29mm models - the Star Orbiter and the Majestic. The former would be OK on E16-8s but it's also OK on E16-6. E16-8 would be too long a delay for the Majestic. So they have no reason to carry that motor any more either. I think I saw F15-8s. They are a perfect motor for the Star Orbiter.
I agree with Fred also in that I wish HL carried E12s.