Bendix 6080s arent cheap, and it might take awhile to find a good pair, but theyre excellent tubes and worth the wait and $
https://www.hifishark.com/goto/65_124342651181/792a2ce4-0d47-11eb-a694-393262613334
Are these the ones you're mentioning? Some Google search came up with slotted vs non slotted, and slotted were better. These look like non slotted (?).