I have a small selection of 3rd party bands from the other side of the Great Wall. They do the job but I’m getting rid of them simply because they don‘t wear that well in the long term. I have a Series5 TI watch with the OEM Silver Link Bracelet and the Grey sport band. My 3rd party are Black link, silver, gold, black and space grey Milanese loop and a few sport loops. I decided to order two Milanese loops (One silver, One gold) from Apple. My silver arrived Monday and I could immediately feel and see the difference. it is slightly heavier/stronger. The finish is better. Great attention to detail. You can see the mesh is much tighter and the edges of the strap are polished so no burrs to snag your clothes. They are not cheap but you get what you pay for.
Having said that I fully realize some folks have budget constraints and if that is the concern DO NOT stretch your budget to the point of collapse just for a watch strap. You will be stressed for no reason and you’ll get a lot of use out of the heart monitoring on the new watch.
If you’re not sure, try a 3rd party watchband to see if you even like the look. There are countless ones to choose from. I bought mine from Paraphonealia and GoStraps. I had no issues getting them, other than slow delivery due to what ever the world is freaking out about this week. Did one exchange with Paraphonealia that went well. Search around. You’ll find what you want. Happy hunting.