Should just make everyone provide their own. It's not that expensive individually.
1 spirit of harmony provides the lotuses for 3 flasks and I seem to get at least 3 spirit of harmony a day just on my main while doing daily quests. Then you have your Tiller's farm where you can get more Golden lotus.
Also In the time it took to get my warlock alt to level 87 I found 7 golden lotus while questing so imagine how many you might find with a level 90 herbalist with a flying mount..
There are lots of ways to get golden lotus so the idea that it costs too much is strange to me.
With only tillers exalted (which you should reach soon in a few days as a raider) you get lotus for 33 hours of raiding per week without procs. If you are an alchemist you get flasks for 66 hours of raiding per week. Seems enough...
Camp rare mobs in Tonlong. One of them (don't recall which one) has the chance of droping a herb container with ~15-20 lotus in it. Given the short respawn timer of rares you could loot several of those containers per week.