Just one, if you're willing to wait 2 months.
When I bought my plane the left recognition light was broken. The recognition lights are bright white lights mounted on each wingtip facing forward, used to reduce the probability of midair collision in poor visibility.
On May 14 I ordered a replacement bulb. The factory immediately began to make one specially for me.
Today it arrived. It was a bulb dangling flywires. With some trepidation I went to the airport and dismantled my wingtip to find out how it would mount. The old (smashed) bulb had flywires with a connector on the end. I went back to my lab from the airport with both bulbs in hand, and moved the connector to the new bulb. Then I returned to the airport and fitted the new part.
Once everything was tidied up I turned on all the light switches and walked around the plane. The recognition lights are now good. The strobes are good. The landing light is good. But the left navigation light (red, for port) is burned out.
Today I ordered a replacement bulb.