This is a replacement for Suzuki part 44348-87420-000.
On my GSF 600 Bandit (2001) this gasket was leaking. So I designed a replacement one which fits well and does not leak (24h from now).
Hint: to make it fit well, apply some grease to it ! It will stay in place when you will be mounting the tap on the tank.
I printed it using cheap chinese flexible filament (TPU, brand "jurui " found on aliexpress). This is supposed to not dissolve or be degraded by gazoline. By the way I ordered a repair kit to rebuild the whole tap: I just hope this printed gasket will live enough ;)

Edit: This gasket did his job for 2 weeks (the time for the brand new gasket to arrive). When I replaced it, it was not degraded: I put it in a jar with some gazoline. One year after, the gasket is still ok: so I think it would have last a long time.

Edit: now Suzuki uses the following reference for the same gasket: 44348-87421-000 . This part is also mounted on many other Suzuki models: DR-Z400 GN125 DF125 GN250 DR650 GSX1200 TU125 TU250 VL125 VL150 VZ800
May also replace Honda, Yamaha or Kawasaki gaskets with the following references:
Suzuki: 44305-48B11 / 44305-17C00
Kawasaki: 92055-1112
Yamaha: 1J7-24512-00-00 (needs resizing)

I ordered a big set of brand new gaskets, you can buy one on my e-store here:
https://www.technocoma.com/index.php?id_product=31&rewrite=fuel-petcock-gasket-for-suzuki-gsf-bandit-600-1200&controller=product&id_lang=2
Get 7% discount with this coupon: BIENVENUE7