Exterior safe "popcorn" texture?

Howdy all, got a question I hope someone here can answer. I'm painting a faux monument style sign, and I want to add some texture to it. Now I've noticed there are other signs in my area, where the sign maker put a "popcorn" type texture on the poles, base, etc. Problem is, I can't figure out what it is?

I've tried knockdown spray texture in a can, and that melted off in the first rain. So did a "textured" style spraypaint.

Oh, and because I know someone will ask, I can't find out from the other sign maker, because the are out of business.

Anyhow, any help or advice is welcome. I'm at my wits end, I've checked with Benjamin Moore, and Sherwin Williams, and they came up empty.

Thanks!

 

Thanks guys, I'll check those out!