According the SCP-738-2 there is at least one way of terminating 682. It's true that SCP-738-2 can be tricky and manipulative but from what I've seen he does not flat out lie, nor would he have any reason too in this regard as he flat out states the request could not be paid for. I believe the reason that the price was beyond paying was simply because the request included the safety of the human race, the planet and the universe.
Enter round two for SCP-826! True the previous attempt failed, to be fair though, test logs show that the cannon can quite easily be changed through the actions of those entering the story world created by 826. I also believe that the argument could be made that the story, and subsequently the creature, were limited by the story itself being too vague and/or the lack of understanding on part of the author in regards to 682.
Assuming that 682 could somehow be lead or tricked back into 826. What if a story was written and reviewed by experts on writing, in where on a planet similar to earths their exists a a platform like device that teleports itself and what ever is on it to the opposite side of the planet. The story would also state that this second location holds a small shrine containing the only book in the world, presumably ensuring the location of 826. This would not be for the saftey of whoever has to go into the story for the plan to work but to keep the book away from 682.
Bring 738 into the story, leaving the door open to bring in 682 shortly after, and and use the teleported to transport to location #2 where the deal is to be struck. Without the hindrances of the original request, which were quite huge to ask for, it is conceivable that the price will be affordable even if still steep, say like five hundred deals a year for fifty years must be made with 738-2 or some of the major threat SCPs, such as the zombie virus, will be released into the world. These deals of course could cause all sorts of issues in their own right.
Now there are a number of contingencies that could be put into place to make this work better, for example SCPs I haven't become aware of yet to be used in conjunction with the others albeit they could be lost in the course of events. Writing another creature like the one from the first story or having the story world densely populated everywhere except for location #2 with creatures that that exist only to try and kill 682, these are merely distraction methods of course.
I also realize that even with everything I mentioned before there are potentially a number of things that could cause this plan to be ill advised, ranging from simple to deus ex machina in how it could go wrong. Still, assuming that the above criteria is met I think its a decent theory. I welcome any thoughts on the matter.