I don't think there would be enough interest to justify a TAS only board. I think a lot less people have seen them than the other series. I don't think they've been seen here at the End of the Universe on TV much past there original run decades ago. TOS has been barely seen here in the past decade.
I bought the boxset for $88 and I think they're now $20. My child likes them and at $20 for 20 odd TOS/TAS stories thats pretty good value for money. Cheaper than buying the novelisations.