You can always thicken( harden) Bore butter by adding beeswax to it. Just heat some up in a tin set in a flat pan with a 1/2 inch of water in the bottom of the pan, to make a " double boiler". When the bore butter is melted( Liquid) add wax. Let it melt so it mixes thoroughly, then remove it from the heat to cool- either in the small tin, or in the container you want to use to store it and use it on the range, or in the field. You can speed the cooling by putting the tin of mixed lube in your freezer for 1/2 hour. How thick or hard it will get will depend on how much wax you add to the bore butter. I have seen recipes for Wax/Olive Oil that use a ratio of 4:1, which makes a pretty hard wax lube, except in the heat.Compared to the Bore Butter that comes in a tube- about the consistency of facial(cold) creams-- and you can see the difference readily.
To test it, put the closed tin out in sunlight, and check it in 4 hours.
Most of us keep these things in our "possibles" bag, so they are not subject to direct sunlight. That keeps them cooler and a bit more solid. But, if you are out in 90 to 100 degree+ heat everything is going to melt- even you. Find some cool place to be, in shade, because I can assure you that all the animals you are likely to be hunting will be doing the same thing.
Even Antelope, who live out in the heat all the time, will seek cooleys and ravines where the ground may be cooler on their feet. You will rarely find Antelope moving around during the heat of the day.