That PSU is proprietary. Because of the size and type you will not be able to find a much larger PSU and certainly not in the 300-500W range. You can install a GPU such as a GT 1030 low profile but if you are determined to install a much more powerful GPU then your only other option would be a case swap. And after purchasing the parts the cost would be well over your $30-50 dollar range.
I want to buy a better psu to install a gpu but not sure what psu to buy because I don't feel like returning it if it doesn't fit. I'm trying to find a psu in the 30$-50$ price range. And the walts 300-500. Please recommend me a psu that will fit.   ***Dell Optiplex 3050 SFF***
Best fitted psu for Dell Optiplex 3050 SFF