Actually, you have a few other options:
1) Negotiate a fee with your agent, and make an offer at 'list price' - 'agent's fee'.
2) Make an offer requesting a rebate (from which you'll pay your agent).
3) Make an offer to purchase the property with 80-100% seller financing, and pay your agent out of pocket.
4) Bury a clause in your addendum, written to override any of the other terms specified in the purchase agreement, that requires either the seller's agent to co-broke or requires the seller to pay your agent's fee. (NOTE: Incidentally, if that seller's agent refuses to submit that offer, kindly inform/remind that agent that you'll inform the board of realtors about his/her refusal to submit your offer, and that s/he could end up losing his/her license over that offense. Keep in mind you'll probably tick him/her off by doing this.)
5) Threaten to walk if that agent continues to balk, and see if the seller's agent relents.