I had your same situation last summer when my daughter got married. I got a fairly expensive ($850) synthetic wig from a reputable wig store and my insurance covered $500 towards it. I used it for work until recently so got my money’s worth. It helped to use a little liner under it to minimize any itching. The ones made from bamboo are the most comfortable and are inexpensive if you order online.
I wore fake eyelashes for the day which the makeup person applied. I asked for a natural look so they didn’t look fake.
It’s not easy being mother of the bride when you’re going through chemo but it beats not being there at all. I wish you the best!!