Just stack some strongish boxes. Use bricks/wooden blocks to stop the bar rolling off.
If you don't have boxes, four 4x4s at lower chest height .A plank of thick ply for the top and some 2x4 screwed together to brace it all (off cuts glued to the ply to stop the bar rolling off) will set you back 25 bucks. When you get your rack you have 2 great sized boxes to jump onto. A tiny bit more work and you can make the two boxes into 6 stackable ones for different jumps
Single leg work
Trap bar is a fine substitute if you get your hips low
I've seen guys go pretty heavy on goblet squats too.
What are you benching off BTW?