terrib
A replacement bulb for your 880 should be part #1880629000.
BTW, what is the serial # on your 880? If you claim to not have changed this bulb in 30+ years, then I know for certain the entire production span of this unit was between 1966 and 1987. Yours is likely a 1970s unit.
Example of serial #s:
On nameplate riveted to the bottom of the motor unit: 880-12345.
On nameplate applied to the back view of the nozzle (by front wheels): 17C-H-44915, 78K-C-23542, K78-C-24357, A87F091331.
~Ben