The venerable GS500 has been in production for long time but not sold anymore in the USA.
Parts are harder to get - so I figured we should make a list of parts retailers with contacts to help folks out. This isn't a recommendation but rather a list of retailers. Feel free to add to the list, and I'll sticky this on top.
US Parts retailers
* Suzuki Parts House : https://www.suzukipartshouse.com/oemparts/l/suz/50d3f2e5f8700230d8b4bff7/2001-gs500-parts
* PartZilla : https://www.partzilla.com/
UK Parts Retailers
* GS500 World - https://www.gs500world.com
EU Parts Retailers :
* CMS NL: https://www.cmsnl.com/ https://www.cmsnl.com/suzuki-gs500_model13447/
Latin America
Africa Parts Retailers:
Asia Parts Retailers:
*
In Australia, the Suzuki dealers are always worth a try. In Victoria 'Mick Hone M/C' still holds some parts
My favorite here in the USA is motosport.com. I also like to get the part number(s) from there and then search them on eBay.
Don't forget your local Suzuki dealer. They can get any of the same parts the Motoport, Partzilla, Suzuki Parts House, etc can get you can will save on shipping in exchange for having to visit your dealer. Its best to show up with the parts numbers you want because it can take forever for the parts counter people to find what you want.