Hello Guinness,
I strongly recommend that you contact two people for helpful information:
1). Al Berger at...
http://www.bergerwerke.com/ His website provides the best resource information on the history of G519 military bicycles from WWII and he sells top-quality reproductions of some very hard-to-find parts for bicycle restorations.
2). Bob Ujszaszi, a CABE member at...
https://thecabe.com/forum/threads/saddle-services-whizzer-pogo-airflo-troxel-streamlined-etc.157107/ Bob is the go-to person for either buying a beautifully restored saddle or having a vintage saddle restored. Given time, I'm sure that Bob could locate and restore a period-correct Persons saddle for you.
And for your info, I kind-of unintentionally ended up building a G519 bike as a tribute to both my late father and to my childhood memories using an 11/4 fork date coded Huffman-built balloon tire bicycle that already had a lot of the same type of parts as used on the military bikes. This project wasn't something I planned on doing but once I got the bike and the idea, everything else seemed to quickly fall into place. Plus, I got lucky finding all the parts needed for this project idea from either the CABE or from eBay.
When I was growing up in the 60's, my father had an olive drab Dayton bicycle that my brother and I called "The Tank." There was no speeding away from him on our small kiddy bikes we had at that time - even for my older brother on his super-sporty 60's Sting-Ray. We understood that our dad's bike was an ex-Army bike from WWII. But that bike is long gone except for our memories. And we think that he probably bought that old bike at an Army/Navy Surplus store sometime after the war.
Pictured below is my father circa 1943 at Camp Barkley, TX, as a 1st Lt, Headquarters Company, 358th Regiment, 90th DIV ...
And this is my completed tribute bike...
I had to use a longer seat post for my 6ft height but other than that, everything else is basically period correct. Repo truss rod parts and pedal blocks came from Al Berger, saddle restored by Bob Ujszaszi, post-war Centipede Grip tires, original blackout Morrow rear hub and a blackout Eclipse front hub sourced from the CABE were used to build the wheels and were repainted olive drab, repo grips and an original Persons seat bag from eBay, also a vintage military-type Bevin bell, kickstand and the correct unmarked wartime Delta headlight. It may not be a real G519 bike and will never be advertised as such but damn me if it hasn't turned out to be a nice-looking tribute bike! Just the thing for local 4th of July parades!
All the best,
Gregory