Just use wider zip ties but don’t cinch down tightly. You should leave slight play at the connection point.

 

As Strega pointed out an ordinary zip tie can sometimes be used.
But sometimes it won't hold the wires quite as nicely as the original clamp had done.
The good thing is those custom clamps were used for mass production and are not strictly necessary now, to be exactly what had been there.

I did a lot of research into this a few years ago and came up with a few universal clamps which can be used in place of nearly all of those custom clamps:

82711-12A70, a large capacity zip tie type clamp which clips to the Toyota standard 7x12mm slot. This is my main "go to".
82711-10330 is almost the same, but for clipping into a dia7mm round hole (common on pre Gen3, and used in a couple of places on the Gen3, pretty much from Gen4 on all clamps used a 7x12mm slot instead.

Here are a lot more part numbers for some other options.
- the zip tie clamps "0.65~2.6t" means thickness of the panel it will be clipped to
- the "dia15COT" means it is designed to hold a corrugated outer tube of that diameter, those COT clamps go onto a steel "tongue" 16.5mm wide 1.2t.

 

For a universal clamp type that is pushed onto a stud, 82711-3F240 (it has a zip tie structure which will accommodate up to a 30mm dia bundle).

 

Lots of times those would come WITH the harness.... but the harness is usually ridiculously pricey so its likely not worth it.

If anything I would go to a junkyard and look for newer vehicles or low mileage crashed cars etc... that might have something useful and harvest those