Try L-Theanine, 200-2,000mg+ (you can mix the pure powder into tea like peppermint tea). It's a harmless amino acid found naturally in green tea in small amounts, and aborts trips via another way besides 5ht2a antagonism. I believe it just quiets the excitation (glutamate) of the brain. I've tested it personally and with other people who all agree it works, and is the least prone to side effects of any other medication administered for such purposes. I was actually trying to test out the combination on someone who uses psychedelic 5HT2-A agonists such as LSD or mushrooms for cluster headaches, to see if they could avoid having to do the "trip" part, I wonder if it'd still help with the cluster headaches. Be an interesting experiment.
You can buy it at Walmart in the health supplement section, or really cheap via bulk powder on the internet with a quick search. Just make sure if you use it for these purposes it doesn't contain anything besides the l-theanine (no green tea or caffeine).