Hi David
Funnily enough I have gone through this recently. I picked up my rifle that came with a single set trigger, which personally I do not like. That is just me though...
So, I managed to source a secondhand standard trigger unit which will be sent to a custom rifle builder I know for reworking. He has assured me that the removal and refitting of a Sako trigger unit is very straightforward.
That being the case and all going well, I will probably put my one up on here for sale. Let me know if it is of any iinterest to you. If not it will appear in the ads.
Further, there is currently NO after-market trigger available for the Sako other than the ones mentioned. If Arnold Jewell make one in the future, I will be first in the queue having used them on other rifles for well over 10 years now.
My rifle-building mate assures me that after he has worked on a Sako trigger, which he says are about the best of factory triggers, the finished product is superb. I am sending mine through to him this week and will keep you posted...