Did you try a U pull it style junkyard? These kinds of places are a great resource for small parts like that. Even better is that you get your "practice run" taking it apart, on a junk vehicle. If you lose something or break something, nothing ventured nothing gained. It is also a great way to save money when replacing these kinds of small parts, as sometimes you pay 10 20 mabye 30 dollars for something like the spring you mentioned. And thats if the dealer can still get the part. As our trucks get older, the supply of OEM style parts gets smaller every year. Try your local wrecking yard, its like a do it yourself crash course in anything you want to learn about your vehicle. AL
If it's a compression style spring, and you could figure out the length, spring
diameter and spring tension, an autoparts place or a fastener place that has
all sorts of fasteners and spring may be able to help,
If you can figure out the length and size, you can buy one cheaply from a fastener place and fashion one by cutting it to length.
It's an idea and that's what I would do, if I had to do it, but I also have a
fastner place right next to me that carries all sorts of springs too.