I've been using the Pulse 450mAh 2S packs with my Beta75X and Eachine Trashcan but they are a very tight fit. It's so tight that the corners of the battery holders are turning white from stress. I ended up cutting them off and drew up a set to print in TPU that holds the stock 350mAh 2S packs and stretches to fit the Pulse 450mAh 2S packs. Any pack comparable in size will fit as well. They add .7 grams of weight and can't be pulled off so you don't have to worry another losing them in a crash. I suggest taking the electronics out to install the holders, they can be installed without taking the electronics out but it is tricky,
There are 2 files, one is for the front and the other for the rear, they're labeled accordingly.
The canopy with a built in adjustable camera mount can be found here: https://www.thingiverse.com/thing:3385166
Update: As requested I added a second version with a slightly thicker box for the battery. The files are: 75X_Battery_Holder_Thick_Rear.stl and 75X_Battery_Holder_Thick_Front.stl
This was printed with .1mm layers and a .3mm nozzle.