If you search for nearer dates it comes up. So it might be that Alaska aren't loading availability that far out.
You could try calling, but I suspect you will be out of luck, if you can see nearby dates but not 10 months out on the website, the agents won't be able to see it either.
Try chaning the dates to find out when they are loading them (possibly 6 months out) and then putting a note in your diary.
Economy is showing as 18000 Avios and £4.30 so not a great use of Avios compared to £107 on a commercial ticket. 40k Avios versus £250 for First (Business)