I am finally getting a Spaulding Palomar 90w SOX streetlight, and I am wondering where I can find a reasonably priced (under $100) lamp for it.
If anyone has any lamps they would be willing to sell to me, please let me know.

If you go the route of eBay, it takes patience. There’s the typical price gougers which will always have stuff, but occasionally a decently priced SOX lamp does get listed. You just have to keep your eyes peeled, which is what I do. A lot of 2 18W just sold for around $60 last week. I got my Philips 90W for $80-ish after shipping / tax.

 Cheapest I could find : https://www.ebay.com/itm/186186183451