I have a GL1 use for filming skateboarding long lense which is great because it has a gnarly optical zoom but i’m in the market for a fisheye lens for it and i was wondering if anyone had any recommendations.

Not fisheye, but they do give more width.

Century Optics (now owned by Schneider) offered a ".65x wide angle converter for the Canon GL1" that was bayonet mount.

The Sony VCL-HG0758 is threaded mount, fits, provides 0.7x. and is much easier to find and likely more reasonably priced.

You should be able to find one on the used market.