Rare and very expensive European Edelstahl V4A.eu stainless 2" (50mm) ones are beautiful but hyper expensive. They did 42mm as well. The rights were sold on after original owner retired/got bored/whatever.
Others have posted recently about ordering and purchasing a set but cost delivered was well over US$1000 I believe and I doubt that included freight.
This
WAS from the old owner/maker's link and product range and prices
that must be 10 years old at least. Expect them to be double now! The link has now died but if you have good search skills you may still find cached versions.
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Finding them is one thing, buying them another matter


Triumph Rocket III, Rocket III Touring and Rocket III Roadster Protection
Tent
Type IV 50mm
18x Pictures: Triumph Rocket III, Rocket III Touring and Rocket III Roadster
Stainless steel guardrail made of 50 mm diameter with connecting tip - 3 styles (09-1110) or (09-1120) or (09-1130) and fixing kit. Hoop is highly polished Stainless steel: V2A - 304L
490,00 EUR incl.
470,00 EUR incl. VAT and without Lamperhalter - ( light brackets)
Order-No. 09-1119
Currently
in stock
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Very hard to source these days, that company appears to sold out or something and the new owners are also crap at replying to emails and may not handle all the product line anymore

Back in march 2016:
I attempted to contact Edelstahl v4A
Link Removed via their website email contact
info@v4a.eu and initially did not receive a reply but after a second attempt received the following reply from an email address titled:
Johann Lamminger with actual address
hlamminger@web.de.
"We have acquired the general distribution for the
Edelstahl Rocket Roadster radiator cover*. The price for the Edelstahl Kühlerverkleidung (High-gloss, polished stainless steel) 109,-- Euros. , shipping charges, 44,--Euro.
Greding Hans"
*
My translation
Note the prices here were for a Radiator grill cover I also enquired about and not the crash-bar.