It seems that a lot of the older bulbs were OEM. I would suspect that for an 8X10 enlarger that the bulb wattage is a minimum of 500 watts since my Durst 5X7 uses a 500 watt opal lamp. The bulb needs to be a bulb for photographic application since the writing on a typical incadescent bulb will lead to printing difficulties as the writing is known to be projected as differing density onto the image.
If it were me and I couldn't find the original bulb, then I would convert this to a single ended halogen of 500 or 750 watts. Depending on whether your enlarger is a condensor or diffusion you may need to design a diffusion grid since the halogen is more of a point source then the frosted bulb.