Closest to what you're asking for are basically "bars with hooks".
Here's a pair from FitBar:
Depending on your needs/goals something like a Metolius Rock Ring might end up being more versatile:
There are a lot of companies that make similar items; if these don't meet your needs, searching for "obstacle course racing training equipment" or "climbing training gear" or something should turn up more options.
There's a lot of options for the make-y inclined, some easier than others. The only caution is that over-engineering/-speccing here is recommended. Nothing with under ~500lb/220kg-ish specs. Use abrasion-resistant cord (like Spectra) or webbing.
I know more than one person (ok, two, but still) people that were seriously injured on make-shift equipment (one paralyzed). Just because we're talking about door-jamb-level heights doesn't mean Really Bad Things can't happen.
Disclaimer-y rant over, but srsly, be careful.