What are all the sources of RARE XL candies?

I am level 44 player, I am interested in PVP. I play GL because I don't have mons built up for UL or ML. I have given my golden bottle cap to Zygarde and I will make it a hundo soon. Now the question is how do I max it out? I can dump rare candies but what about rare xls? I have around 156 of them and I have NEVER used them anywhere till now. How do you all collect rare XLs? I know raids are the source, but I don't see to get that many. Any other way to get XLs? Thanks in advance.