I was able to reconstruct my seller fees from emails on the successful sales of tickets. As to the buyers fees, I can see the aggregate amount for a month from 1099-k by subtracting the sellers fees and the actual money sent to me by TicketMaster--but cannot determine how they actually allocated the aggregate monthly buyers fees to individual transactions. Seems like the best approach is to allocate by sales amount (as I think that's generally how they charge), but you'd have to be careful on gain sales to make sure to show the right amount of profit. The biggest difficulty is increasing the proceeds by the amount of the allocated buyers fees.
By the way, the IRS updated information on this issue:
See general Q/A 3 & 5:
https://www.irs.gov/pub/taxpros/fs-2023-06.pdf
