Your spec is incomplete.
You need to check the thread pitch, although with a major diameter of .210 the only standard pitch that fits would be 28 threads per inch. A 12x28 UNF thread, which is the common standard that's closest to your.210, has a major diameter of .216".
Overall length and thread length are not terribly important in nipple design, but cone height is. Cone height is the distance from the tip of the cone to the nipple bearing surface, or the surface that contacts the cylinder when screwed in place. Unfortunately that's rarely specified. Using your .475" overall length I'm going to guess that TotW's PCC-A, PCC-I or PCC-S are the best bets to fit your application; they're .501" overall (at least they were the last time I measured any).
But, your best bet is to call TotW and ask them. Get your thread pitch and cone height first so you can tell them exactly what you need. And be prepared to compromise.