I know for sure that anything for .54 cal. is hard to find, it's a great caliber but I think it was the inline craze that killed it. Better get a mold and some lead. Track of the Wolf will have anything else you need. At US $ of course.
Order yourself a 54 caliber great plains bullet mold 460 grains and be done with it. That bullet will kill anything in North America at 100 meters save the great bears and it will probably take them as well as long as your buddy cant run as fast as u can.
.......HP i do believe mans hollow point bullets, and non HP means solid tips on the bullet.
I am currently shooting a double saboted 357 lead bullet and this seems to be the ticket