My go-to place for electrical parts these days is Ace Hardware. We're not talking McMaster-Carr, but they're pretty well equipped.

I went to Ace a few weeks ago to buy parts to A) rewire a lamp, and B) replace the receptacle of a heavy duty extension cord which fried dealing with the short circuited lamp. There was a bundle of measured, priced zip cord by the reels; I thought I'd do a good deed and buy it. Longer than what I needed, but spares are always good. The guy at the counter gave it to me for the price of only what I intended to buy!

Tru-Value outlets might have the same sort of inventory.

Good auto parts stores are a source for lamp housings and switches.

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NAR #27085 - Oregon Rocketry - SAM