I found a link to a Lewmar catalog that shows older traveler hardware in exploded parts diagrams. The end stops and its internal sheave can be clearly seen on pages 14-15. There is no clear diagram for the the traveler car, but there is a Size 2 genoa car on pages 12-13 that appears to have the same base. The size of the sheaves and the center hole are not listed, although parts numbers are listed. (I searched on the Lewmar site for the sheave part number but nothing came up.)
https://www.lewmar.com/sites/default/files/Ocean Spares Data.pdf
I also found new Lewmar double sheaves and cam cleats that look like they would mount onto the end stops, SKU LW29172014, $132 each at APS, but for that money I might as well get the upgrade kit for $500, if I can move the cam cleats to the ends.
The sheaves on the Lewmar end stops use the mounting screws for an axle, with roller bearings (bushings, really) that fits around the screw and inside the sheave. Finding a replacement sheave/block with a bearing insert that will will be difficult.
On the other hand, I can see from the parts diagram and the pictures sent by stevemitchell that a tear down, cleaning in solvent, adding light grease (as with a winch bearing), and using smaller diameter line might do a great deal of good.
On my boat I could see that the traveler car had plastic ball bearings, but I couldn't see how the end stops were assembled, so I have never added any grease to any of the traveler parts, just hosed them out thoroughly every spring and during the season when it looked dirty. I also applied some dry Teflon or other dry lubricant to the track and cam cleats.