There are a few different ways to get your calibration file for your ECU and this goes beyond the scope of what you can do with hpt.
One way is to read the calibration directly from the ECU. This requires some specialized equipment that is readily available and relatively affordable. But if you're after only one file you do not want to go this route.
Two is you get the CUW (Calibration Update Wizard) file from the Toyota TIS. This would cost you $20 for a 48-hour subscription to TIS. Then there is a free online conversion tool that will translate the CUW file to a binary/hexdump. From there I don't know how you translate it to hpt.
The third way is to purchase the binary/hexdump from BitBox. They have a catalog of every Toyota ECU. Their cost per file is not too unreasonable.
I don't know how a .cuw or .bin correlates with a .hpt. All three file types contain the exact same information, but in different formats. I have not attempted to decode the .hpt format. The .cuw is an obfuscated/lightly encrypted format that Toyota uses to protect its intellectual property, but it has been cracked. The .bin is a standard format that most tuning professionals use and it is the format actually stored in the ECU's memory and it can be flashed directly to the ECU with standard tools.