The CA3280 is really hard to find in these parts, and as the Sequential Prohet 5 and 10 use lots of them as their VCA's, and they are prone to failure in these machines, I have been trying to get some in stock. Farnell and RS have none, so I guess I need to look overseas.
I have no trouble getting CA3080's and I go through lot of them, these pop up everywhere, in some Moog VCF's, ARP's, Roland SH7's, EMS stuff etc. I change lots of dead ones throughout the year in my service shop.
I have no problem finding the transistor arrays like CA3046 and CA396's, Jaycar have some, as do Farnell. I changed one the other day in a Moog Prodigy with A dead VCO.