I have had good luck with several products here; https://www.1000bulbs.com/product/204208/CMS-C9SWW.html

They have an array of temperatures and has an old look. I bought 1000' feet of their spool and bulbs and have been using for about 7 years with zero issues. Only bulb to go out was because I dropped it on some concrete. I also did this after a couple years of what turned out to be single use lights from big box store.

It's not cheap but not sure what your budget is. At least you can get some mileage out of them.

I really like the look of C9 bulbs as well, but incandescent strands these days are all pretty cheaply made - and actually, anything you buy in a typical big box store I think probably isn't going to last more than a season or two in good conditions. I don't have specific recommendations - all my lights are addressable RGB LEDs. I would look for commercial sets, which I would suspect are designed to be more durable for longer-term use.