There are several sources for 1/350th scale standing figures.
2D photoetch (pre-painted). I'm pretty sure Verlinden did this first but there are sets from several companies out there.
2D plastic. Tamiya and (I think?) Hobby Boss have sets available for WWII battleships.
3D printed plastic/resin. You can find multiple sets at Shapeways but I haven't ordered any, yet. Shapeways can be a great resource but they can also be a solid pain to order from.
Keep in mind that a 1/350th scale standing figure is about the size of a small tick.
I added a topside PO and a duty officer to my FLT III 688 many years ago and they're still hanging out.
I glued their feet to the deck by dipping their shoes in some Elmer's Rubber Glue then quickly stuck them in position while the glue was still wet. The glue is thick enough to keep them standing tall until it dries and you don't have worry about the glue fogging the paint.
With details this size,
plan that you're going to lose at least one of them at some point.
The rubber glue is easy to remove if this happens.
Now that I think about it, the rubber glue would also work well if you're installing stuff like photo etch side rails and small antennas.
Meanwhile, check that Ebay link in the first post if you're still on the fence about ordering it.
As of today (5/8) there are still a butt ton of those kits available from mainland China.