Tickets to Dropkick Murphys concert in Boston?

I was hoping to go to one of the Dropkick Murphys concert in Boston from March 16-18, but all of the tickets are sold out. It seems like the only remaining option is getting a ticket from some online vendor or a scalper for more than twice the ticket price. I've considered going to the concert at UMass in Lowell, but I would much rather go to one of the concerts in Boston. I'm not particularly keen on the idea of paying 90 dollars for a ticket, anyone have any suggestions?