HME T-Post Fence Step

Mine is slightly different, but as long as it's sturdy and fits the posts, that one should work fine.  I highly recommend using it in conjunction with a post cap so you can support much of your weight with your arms just in case the step slips or breaks while you're straddling the fence.  The cap needn't be anything fancy, just something to protect your palm from the narrow and often sharp post top.

This does not seem quite right…

T Post Caps Safety Orange for T Posts and U Posts, 15 pcs. Clip for Wire and Tape, Ends of Tent Stakes, Rebar, Pipe, Livestock Fencing Tech Team https://a.co/d/hpzZmpI

Maybe more like these:

Stake SAFE, T-Post, Re-Bar3-6, Small U-Posts, White,10 count https://a.co/d/5lGKpFY

The problem with those is that they force-fit on the post.  You want something that slips on and off easily so you can take it with you -- it doesn't have to be snug at all.  I repurposed an old die-cast floodlight socket, but almost anything that slips on and off and offers a smooth flat top for your hands to rest on will do.

You could probably modify one of the Stake SAFE units with a Dremel tool -- or even a sharp chisel -- to remove the internal ribs that grip the post.